I make potholders out of test blocks. As far as what goes inside, I use old dish towels or mattress pads. Anything that is 100% cotton. It just depends on the thickness of the filler how many layers I use. I find that most burns are from too small size and/or the potholder getting wet. I never make mine smaller than a 9 inch block. Old cloth diapers work real well too. But then I buy cloth diapers for every day dish towels when I can find them. If you are a thrift store shopper old linen table cloths are great for dishtowels and filling for potholders. I even have used a couple for quilt backs.