I used a 2' by 4' 3/8 inch piece of plywood. To protect the wood from steam, I covered it with foil (also reflects the heat), then used a double layer of cotton batting and stapled a muslin cover over that. It makes a nice size for ironing pieces of fabric, and is nice and firm for pressing blocks. I tried one of the commercial mats but it wasn't firm enough for my taste. This is place on whatever table, picnic or otherwise, I am using for a work surface.