Velcro has a loop part, and a hook part.
The loop part is made up of soft tiny loops, and the hook part is stiffer and hooky.
When you press them together they stick.
Think of teeny fish hooks caught in felt. You know what felt is right?
PM me your address and I'll drop some in the mail to you.
I have leftovers from a Holga mod I did some time ago.