I love French Seams!
They are quick, simple and clean. Especially nice for kids clothes that need to endure lots of wash cycles. This is a perfect technique to use when working with fabrics that tend to fray heavily or if you just want a professional, polished finish without a serger or overlock stitch. With a French Seam all raw edges are completely enclosed. No unraveling.
The technique may at first feel counter intuitive but once you've seen it (or sewn it) you'll see it's quite simple and makes perfect sense. There is only a bit of extra math involved in order to determine your finished seam allowance. I will explain how to sew a French Seam if your pattern includes either a 1/2 or 5/8 seam allowance (SA).
If 1/2" SA included - First with WRONG sides facing sew a 1/4" seam.
5/8" SA included - First with WRONG sides facing sew a 3/8" seam.
Next carefully trim seam allowance to 1/8".
Open pieces so that right sides and seam are laying face up, press seam allowance neatly to one side.
Turn again so that RIGHT sides are now facing, press.
Stitch 1/4" from the edge. Finally turn right sides out and voila! You have a completely encased French Seam.