I've used this quite a number of times. It's ragged around the edges as can be seen, but shoots fine. The webbing is from a discarded child seat, I think, and it is very nicely slippery lengthwise but not transversely. (That might help with release in some way.)
Step 1: Cut denim
Step 2: Add webbing
My first attempt had the webbing come somewhat undone after shooting. So I just added glue where more glue was needed.
Now it's working fine. No finger pain. Webbing is a bit ragged around the edges (I can't melt the edges as that would interfere with string release) but it works. Don't know how long it'll work, but when it gives out I can either make another or just buy something, and I just wanted this to tide me over for a while.