I’m not affiliated with Klum House, I’m just a big fan of their designs and their company. I remember first seeing Klum House bags years ago when I lived in Phoenix and thinking, “I should really learn how to sew so I can make one of those bags,” and also, “Portland seems like such an incredible place to be an artist/maker.” Years later, after I moved to Portland, took a Learn to Sew class at Modern Domestic, and bought a sewing machine, I promptly ordered my first Klum House kit. Since then, I’ve made almost all of their bag patterns, but I still felt intimidated by the Slabtown.
I’m so grateful that Ellie from Klum House gifted me her Slabtown online class to help me prepare for the Klum House Bag Lab I taught at Modern Domestic. Ellie’s classes are full of excellent tips and demos that helped me build skills and confidence as both a sewist and instructor and I highly recommend them! I encourage you to try the Slabtown if you’ve been on the fence about it—it’s truly an heirloom project you’ll feel so proud of. If you’d like in-person support, I’ll be teaching additional sessions of the Klum House Bag Lab for the foreseeable future. It’s so exciting to be able to teach a class that centers on such a meaningful milestone in my sewing journey and I’d love to have you join me!
Pattern
- Klum House Slabtown Backpack (skill level: advanced)
- Need support? Check out Ellie’s online Slabtown course.
Supplies
Klum House offers Slabtown kits with pre-cut leather and hardware (what I used), full maker kits with your choice of colors, and an essential tools bundle.
Fabric & Interfacing
- Exterior fabric: Merchant & Mills Organic Cotton Dry Oilskin in Black (245 gsm / 7.2 oz) purchased from Modern Domestic.
- Accent fabric (exterior pockets): Merchant & Mills Organic Cotton Dry Oilskin in Oxblood (245 gsm / 7.2 oz) purchased from Charlotte’s Webbing.
- Lining fabric: Core Fabrics Sandbox Check Print Organic Cotton Canvas in Cream and Brown (205 gsm / 6.0 oz).
- Pellon SF101 Shape Flex Fusible Interfacing to add structure to lining fabric
- Pellon 805 Wonder-Under Fusible Web to fuse lining fabric together so the inside of the front pocket would show the right side of the printed fabric
- Pellon FF77 Flex-Foam for the padded laptop sleeve that I added
Leather & Hardware
- 1 1/8” and 3/4” wide leather straps (8–10 oz) in black
- Leather scrap piece (8–10 oz), leather washers, and leather zipper pulls (5–7 oz)
- 2 x 12” brass YKK #5 zippers in black
- 24 x medium tubular rivets (you’ll need 4 additional rivets if adding the felt pad expansion)
- 3 x line 24 snaps
- 2 x 3/4” center bar buckles
- 2 x small double cap rivets (only appropriate for zipper pulls on this bag)
- 1 x 3/4” metal D-ring (I added a key ring)
Notions
- Merino wool felt-padded backpack straps expansion kit with leather weld and glue spreader (optional expansion)
- 1” wide cotton twill tape for binding inner seams
- 3/16” double-sided leather tape
- Leather pen
- Walking foot, edgestitch foot, and regular presser foot
- Schmetz 100/16 Topstitch needle
- Jean-A-Ma-Jig or hump-jumper
Tools
- Granite slab, poly punching board, and bakelite mallet
- Rotary punch or 1/8” drive punch
- 3/4” and 1.5” round strap end punches (if cutting straps to size yourself)
- Tubular rivet peening tool
- Line 24 snap setter and dot anvil
- Double-cap rivet setter (if switching out zipper pull rivets)
- Rivet removal tool for fixing mistakes
- 1/4” alphabet stamps for customizing leather
Modifications
Interfacing
- Even though the Merchant & Mills dry oilskin is lighter weight than recommended (7.2 oz versus 9–12 oz), I did not add any interfacing or stabilizers.
- Note that oilskin is not compatible with fusible interfacing because of the wax coating, but it could technically be used with sew-in interfacing.
- Since I used a lining fabric that was considerably lighter than what was recommended (6 oz vs. 10–12 oz), I added two layers of Pellon SF101 to most of my lining pieces. The only exception was the area where I attached the foam laptop pocket—I only used one layer of SF101 here (but I still applied two layers on the bottom “T” section).
Front Pocket
- If you choose a printed fabric for your lining, the wrong side of the fabric will be visible on the inside of the front pocket. I cut two Front Body Lining pieces and used Pellon 805 Wonder Under to fuse them wrong sides together so the print showed on both sides. I think I interfaced one of the pieces with a layer of SF101 before fusing them together but I didn’t write that down.
- I made a slip pocket that finished to ~5.5” square, then edgestitched it onto the Front Body Lining. I positioned the pocket about 2.25” from left edge and 3” up from bottom edge. If I were to make this bag again, I’d lower the pocket 1–2” and move it to the right ~1” so it’s easier to use the pocket without my hand brushing along the top seam.
- My stitch line attaching the pocket is visible from the interior main compartment of the backpack. This doesn’t bother me, and I figured the pocket would be a bit sturdier this way. If you don’t want the stitches to be visible, you could attach the pocket before fusing the two Front Body Lining pieces together.
- I also added a D-ring to attach my keys. I cut a 2 1/8” wide strip of lining fabric along the length or crosswise grain (not the bias) and used a 1” (25 mm) bias tape maker to make double fold tape. I edgestitched along the long edges to secure. I folded it in half (aligning short raw edges), placed it through the D-ring, and basted it along the top edge of the Front Body Lining so that the D-ring hangs about 3” down from the top seam. I trimmed the excess tape and secured it in a later seam when attaching the roll-top.
Quilted Laptop Pocket
- I added Pellon Flex Foam to the Back Body Lining (within the main 14” x 15.5” rectangle, not the bottom “T” section). I positioned the foam about 2” up from where the cutouts began to avoid the boxed corners. I also ensured that the foam did not fall within the top or side seam allowances to prevent bulk.
- The foam rectangle I used ended up being about 11” wide x 12.5” tall, but those dimensions were largely dictated by the piece of foam I had in my stash since it was out of stock at my local stores. Be sure to adjust the dimensions as needed to accommodate your device.
- I basted the foam with Wonder Tape and then quilted the two layers together (I did not add a backing fabric). I quilted diamonds by following the grid intersections printed on the fabric. I only quilted the main rectangle, not the bottom “T” section of the Back Body Lining.
- I cut out a smaller rectangle out of flex foam for the front of the sleeve (~10.5” wide x 12” tall). Again, adjust the dimensions as needed so that it is large enough to wrap around the thickness of your device with enough room for sewing it onto the back panel.
- For this piece, I quilted the foam with lining fabric on both sides, then bias-bound all four sides and edgestitched the laptop sleeve onto the Back Body Lining.
Final Touches
- I switched to double-cap rivets for the zipper pulls ONLY since I don’t like how it feels when I catch my fingers on the the prongs of the tubular rivets. Note that double-cap rivets and tubular rivets are NOT interchangeable—the latter are much stronger and the appropriate choice for backpack straps and other areas that have to withstand a lot of force.
- I stamped “kalimera” on the handle (good morning in Greek).
- I stamped “it all counts” and “Jan 2025” on the interior backpack strap reinforcement piece.
Sewing Notes
- Dry oilskin is a wonderful alternative to waxed canvas for folks with sensory sensitivities. I love the look and practicality of waxed canvas, but I really disliked the feeling of wax all over my hands, legs, and machine after making previous Klum House bags. The Merchant & Mills dry oilskin is easy and pleasant to work with.
- FYI: the black colorway does collect lint and cat hair 🤷🏻♀️
- The oxblood colorway is a gorgeous muted purple-brown that my camera struggled to accurately capture. The pictures on Merchant & Mills are a good representation of how the fabric looks in person.
- The lining fabric is super cute but I think the pattern was printed off-grain, making it difficult to cut along the grainline AND pattern-match.
- Since I used lighter weight fabrics for both the exterior and lining than recommended by the pattern, my backpack has a softer look than those made with Klum House waxed canvas, but it still holds it shape well and is comfortable to use. I’m not sure how well my machine would have handled heavier fabric, to be honest—it seemed like it was approaching its limit while I was sewing the side seams and boxed corners.
- I used two strands of all-purpose thread for topstitching the oxblood fabric and one strand of heavier weight Mara 70 when topstitching the black fabric to compare the topstitching techniques suggested in the pattern. I used all-purpose thread in the bobbin for both. My machine seemed to perform better with the single strand of Mara 70, so that’s what I’ll use in the future.
- You’re going to be spending A LOT of time rethreading your machine during this project as you switch between all-purpose and topstitching thread, but the final result is worth the effort.
- I ordered the leather and hardware kit from Klum House because the 1 1/8” wide leather straps were out of stock. It’s very convenient, but note that you may still need to have some tools on hand and do some additional prep work:
- I needed to re-punch (or widen) most of the leather holes from the wrong side so the tubes of the hardware would fit through.
- I had to flatten the leather washers with a mallet, but even then they seemed too thick for the post lengths of the hardware included. The washers appeared to be 8–10 oz, but the pattern calls for leather washers that are 5–7 oz.
- I was able to make the thick washers work for all of the hardware except the line 24 snap on the middle of the rolltop. Even after a good amount of smashing, the leather layers were too thick for the cap to mushroom over the socket securely. I ended up having to order more line 24 snaps and messed up several before finally getting a good set. I wish I had thought to substitute a 5–7 oz washer instead, but I just assumed I should use what came in the kit. I ended up needing an extra set of hands to hold everything in place and eventually ditched the dot anvil to reduce even the tiniest bit of movement. I have a dent on the cap, but it’s set and that’s the end of it.
- The felt-padded backpack strap expansion was very simple to do and elevates the look and comfort.
- The instructions for shortening the adjustment straps to fit your body were easy to understand, and I’m so glad that Klum House updated its kits to accommodate larger bodies by default.
- I was concerned about whether the side pockets would be functional without elastic, but they fit my water bottles perfectly and feel secure. Any bottle that can fit in a standard bicycle cage should be fine.
- Remember to case (translation: wet/rehydrate) your leather before stamping to get a good impression. I use water in a fine-mist spray bottle.
Notes for Next Time
- Substitute the line 24 snap attached to the middle of the rolltop strap with a magnetic snap rivet for extra convenience. I do like the line 24 snaps for securing the rolltop to the sides of the backpack, though they can be a little difficult to close.
- Adjust the position of the added slip pocket as noted above.
- Try using thinner leather washers.
Keep In Touch
Thanks very much for reading! If you’d like in-person support and instruction, please sign up for my classes at Modern Domestic or reach out to schedule a private lesson. If you have any questions, feedback, or corrections regarding this post, please don’t hesitate to contact me!
Further Reading
All content (including photographs and text) on this site ©2024–2025 Aliya Hoff-Vanoni. All Rights Reserved. Do not use or reproduce without written permission.