Flat felled seam
The flat felled seam is a double topstitched seam, which encloses the raw edges. Join the fabrics wrong sides together, using a 5/8" (1.5 cm) seam allowance. Trim one edge of the seam allowance to 1/4" (0.7 mm). Press seam allowance to one side with wider allowance on top. Wrap the wider seam allowance around the 1/4" allowance, enclosing the narrower seam fabric edge. Press flat. Topstitch close to the edge of the folded fabric.