I thought this was a silly idea when it occurred to me but it was too easy to make these handles, nest the bags, and try it. Now I have a bunch of them around because I found them quite sturdy and re-re-reusable.
Step 1: You will need
8" Velcro - both hook and loop parts
a bunch of clean enough reusable same size plastic bags
Instead of sewing, you could use iron-on adhesive if you have one that's strong enough. Or you could use sticky back Velcro. I don't have much experience with these methods for this kind of project.