I wrapped a yard bag around a 2x4 piece of plywood. Then I covered it with cotton batting and then canvas and pulled it all tight before I stapled and then sprayed the canvas with water several times until it shrunk really tight. I also made some smaller boards from the scraps from the 1/2 sheet of plyboard. I made a muslin pillow case type cover so I could take it off and wash it to keep my canvas clean. Because it does not have much padding, it keeps the fabrics from stretching when you press. I love it and have given several of the smaller boards away. You don't need insulbright. The reason I used the heavy duty yard bags was to keep the moisture out of the wood in case I steamed.