A nice aspect of using the pink (or blue) insulation panels from the hardware store covered with felt or flannel is that they are heat tolerant, so you can actually iron on the design wall (if it is securely mounted to your wall). I often find that handy when I'm working with a pieced backing-- very large to manage on an ironing board. I also sometimes can layer and baste a smaller project on the design wall, as I find it easier to work on a vertical surface than to crawl around on the floor.