Flat Felled Seams are a type of self-enclosed or finishing seam.
It is a great seam to use for jeans, pants, children’s clothing and more rugged type clothing as it helps reinforce the seams. Basically it is for seams that have a lot of stretch, tension, or stress on it (i.e. yoke, crotch or butt seams in pants).
That being said, it is a seam that is finished on the right side of the fabric, so choose thread color wisely. So here goes….
1. Take your two pieces of fabric and place them wrong sides together, stitch (in this case I was using a 1/2″ seam allowance) and then press seam open.
2. Trim one side of seam to 1/8″ and fold the opposite side in to meet seam allowance, press.
The trimmed seam (on the right) is the part of the seam that will be enclosed, so make sure you are consistent in which side you will be finishing the seam. For example, in these pictures I am attaching the yoke to the back of a pair of shorts and I want the seam (and ultimately) the topstitching to be pressed up towards the yoke.
3. Press folded seam over to enclose trimmed seam, topstitch 1/16″ from edge.