Start with fabric of your choice , I used about an 8" square. I purchased a roll of that foamy, for lack of a better work, shelf liner. It's kind of like rubber, but lighter and really does grip. Cut the same size as the fabric.
Then pin right sides together and sew around the outside using 1/4" allowance. Leave an opening big enough to turn it right side out.
Trim the edges and corners.
Turn the square right side out.
Time to start using those scraps.