I made pot holders for Christmas gifts I cut 2 blocks right sides together and sewed around them leaving opening to turn. After I turned and pressed I put this on top of an old mattress pad and cut around it. I then rolled the mattress pad like a jelly roll and stuck in the opening and spread it out inside. (Make sure you match the end of the fabric with the pad so it will fit properly. I then hand stitch the opening shut. Top stitch around the pot holder about an inch form the edge. By cutting the mattress pad after it is sewed there is less bulk in the seam and easier to turn. They last for a long time.
Jothesewer