How to Sew a Slot Seam

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The correct seam finish will help your handmade garment hang better and last longer. Specialty seams are functional, while also adding value to a garment. A slot seam is a decorative technique used on pockets, blouses, dresses, jackets, and coats. This unique seam finish will give your designs a tailored touch with an element of surprise.

We used two colors of printed fabric to make learning easier, but you can use matching fabrics when you make slot seams on garments.

Step 1: Cut a piece of white cotton printed fabric 1 1/2 inches wide by 8 inches long.

Step 2: Cut two pieces of yellow cotton printed fabric, each 3 1/2 inches wide by 8 inches long.

Step 3: Using tailor’s chalk, mark a 1/2-inch seam allowance line along the long edge of each 3 1/2-by-8-inch fabric piece.

Step 4: (A) With right sides together, match up the seam allowance edges. (B) Pin the layers together along the 1/2-inch seam allowance line.

Step 5: Sew the 1/2-inch seam allowances together along the marked line with your sewing machine, using a basting stitch of 8 stitches per inch. Then, clip the thread ends.

Step 6: Press the stitched seam allowance flat on the wrong side, using steam. 

Step 7: Open the seam allowance, and press it flat with steam.

Step 8: Turn the piece to the right side, and chalk a stitching line 1⁄4 inch away from the seam, on both sides of the piece.

Step 9: Arrange the seamed piece with the wrong side facing you, then position the 1-1/2-by-8-inch fabric strip along the seam allowance, also wrong-side up. Make sure the smaller strip is centered over the seam and lines up at the ends with the larger fabric piece.

Step 10: Carefully flip the pieces over, and place the stacked layers, right-side up, on a clear plastic ruler. The ruler will ensure that you only pin the pieces you’re working with.

Step 11: (A) Pin the layers together, inserting the pins perpendicular to the seam. (B) Once the pieces are pinned together, turn the stack over to check that the smaller strip is still perfectly centered over the seam and aligned at the ends.

Step 12: With a sewing machine, stitch along the marked chalk lines on the seamed piece, removing the pins as you sew. Use a stitch length of 10 to 12 stitches per inch, as this will become the seam. When you reach the end of one line, finish the seam, turn the piece, and stitch the second line.

Step 13: (A) With a steam iron, press the stitching flat on the right side. (You’d use a pressing cloth to protect the fabric if the slot seam was for an actual garment.) (B) Flip the fabric piece over to the wrong side, and press with steam.

Step 14: Using your seam ripper, carefully remove the basting stitches, taking care not to tear the fabric as you rip the threads.

Step 15: Position your fingers underneath the slot seam, and remove the basting threads using a pair of tweezers.

NOTE: Another option for removing the basting threads in Step 15 is to use a Seam-Fix seam ripper (available at craft stores). Just loosen the threads with the rounded, eraser-like end, and then pick the threads out with your fingers. Feel free to remove the threads using whichever method you find easier.

Francesca Sterlacci is a New York-based author, fashion designer, educator, and founder of the University of Fashion, an online fashion design video library. This is excerpted with permission from her book Sewing: Techniques for Beginners (Laurence King Publishing).