|I always make my own shoulder bags, so the strap is long enough. Normally I make purses from leather, but the new trend toward fabric bags is fun. I didn't like the look of a flat strap made of fabric, so I experimented with yarn to 'stuff' it, making it nicely padded, rounded, and beefier.
I decided how wide I wanted the strap, and cut the fabric 4 times that wide, then folded/ironed like bias tape, so the strap had 4 thicknesses of fabric. Topstitched close to each edge. Then, using several strands of rug yarn, a few inches longer than the length of the strap, I fed the yarn through the middle of the strap with a big safety pin [like inserting elastic into a casing]. First, I machine sewed across one end of the bundle of strands of yarn to secure them together, and so I'd have the stitching for the safety pin to grab. The number of strands of yarn is decided by trial, as much as the strap will hold. After feeding through the strap, I trimmed off the stitched end and any excess yarn, then it was ready to sew into the bag.
The surprise when I was done...the strap had a fancy ruched look, very pretty!