Slot Seams – How to Sew a Slot Seam the Easy Way

Slot seams are a seam that is decorative with a pop of color inserted underneath. They look a little like a tuck or pleat but are constructed slightly differently by creating folds on either side and stitching a piece of fabric underneath. Slot seams are common decorations on shirts and dresses, and are easy to sew. Although slot seams look advanced, they are surprisingly easy to sew once you understand the construction method. In this tutorial, you’ll learn how to sew a slot seam step by step, including a faster beginner-friendly method and tips for choosing fabrics and seam widths.

What is a Slot Seam?

The slot seam is a functional and decorative seam very similar to the lapped seam. The difference is that a piece of added fabric is placed between both sides of the seam edges of the lapped fabric.  The insertion of a fabric piece behind the lapped pieces adds extra strength and a contrast to the seam. 

If you are learning decorative seam techniques, explore the full types of seams guide to compare different decorative and functional seam styles.

Slot seams add a tailored look to a garment. It is used to decorate pockets, jackets and coats, dresses, and blouses. It is a fun seam to master and use for an extra pop of color. The slot seam will not add width to the seam, as you will see when you try this decorative lapped seam out.

The backing used to create the slot can be a different color or texture, or the same as the garment. The slot creates a decorative slit in the seam and is purely a design feature.

Where are Slot Seams Found? This slit may be down the leg or side seam of a garment. Another common place to find slot seams is down the middle of pockets.

How to Sew a Slot Seam (Step by Step)

The distance from each side of the seam is entirely personal and depends on the overall look of the garment. Slot seams are often used to show a flash of color in sporting tracksuits when team colors need to be on show. These steps will help you make a sample slot seam before trying this type of seam out on your garment. Keep the sample as a reference for any future slot seams. Steps to follow to make slot seams:

1. Choose and Cut Fabric

Choose scraps of contrasting colors to make your practice sample. This sample uses pink for the main and green for the contrast strip of fabric. 

• Cut a piece of contrast fabric (green) 1 1/2 inches (4cm) wide by the height of your main fabric.
• The contrast fabric width needs to be at least two times your seam allowance.

2. Mark Seam Allowances

Take tailor’s chalk or a water-soluble marking pen and mark a seam allowance line along the length of each of the main pieces of fabric.

• The reason that we mark the seam allowance is that when finishing the edges in the next step, some of the seam allowances may be removed.
• In order to sew slot seams, the seam allowances must be at least 5/8 inch (15mm). Adjust so you have a wider seam allowance.

3. Finish the Edges

Finish the edges of the seam allowance you have marked. Also, finish the edges of your contrast color. If you are using a serger, just trim the minimum amount you can.

4. Machine-Baste the Seam

Place the main (pink) fabric right sides together. Now using a basting stitch or the longest stitch length on your machine, stitch the seam. Do not backstitch because this line of basting will be removed. Press this seam wide open. Set this piece aside.

5. Mark Contrast Slot

Mark the middle of the contrasting (green) piece by folding and finger pressing just to guide you when you match this piece to the basted seam.

6. Align

The seam of the basted fabric is going to match the finger-pressed seam line just to get the smaller piece, the slot piece, to fit accurately with the two pieces of the lapped effect. Place the smaller piece of neatened fabric under the larger piece with the seam you have basted running in line with the finger-pressed line marking.

7. Stitch Either Side

At this point, you will be sewing down either side of the seam line that has been basted together. The wider the distance you choose to sew from the basted seam, the bigger the show of color from the slot. 

Sew your seam on either side of your basted seam. The width of the seam must not be wider than the slot fabric otherwise, the fabric will not be caught in the seam.

If you have time to play around, then sew a couple of samples using different widths. You will sew a straight stitch on either side of the basted seam. This stitch is sewn on the right side.

8. Remove Basting

Now you have completed the stitching, it is time to remove the basting down the center. Take a seam ripper and gently remove the basting stitches. 

The stitching line down the center comes undone. It reveals the slotted fabric, and the stitching down the side keeps it all in place.

Faster Slot Seams

If you don’t need to be as precise with your seam allowance there is a quick and easy way to achieve the same look.

1. Finish the raw edges of the main fabric and the slot fabric.
2. On the wrong side, press over the seam allowances of the main pieces. Press the contrast in half to mark the center.

3. All with right sides facing up, place the main pieces on top of the contrast slot. The edges of the main pieces should align with the center crease in the slot.

4. Stitch down either side of the folded edges by 1/4 inch (6mm). There is no unpicking needed with this method. The trick is to make sure the edges are aligned before you sew and use lots of pins, so nothing moves as you sew.

Slot Seams vs Other Seams

Seam Type	Main Difference
Slot Seam	Decorative contrast fabric underneath seam opening
Lapped Seam	Overlapping seam without contrast insert
Welt Seam	Flat seam with topstitching
Flat Felled Seam	Fully enclosed durable seam
French Seam	Delicate enclosed seam finish

Slot Seam FAQs

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Decorative Slot Seam – In Conclusion

The slot seam combines a decorative flash of color with overall seam strength. It is a great seam for the side of hard-wearing outdoor clothing. The show of color gives the garment a point of interest and sophistication. Once mastered, slot seams can be used to create striking design details on jackets, dresses, sportswear, pockets, and many other sewing projects.

Different Types of Seams

• Plain Seams
• Open Seams
• Closed Seams
• Princess Seams
• Bound Seams
• French Seams
• Grading Seams
• Welt Seams
• Serged Seams
• Pinked Seams
• Double Stitched Seams
• Flat Felled Seams