At my guild meeting Thurday night, our speaker, Ann Turley, told us she uses insulation board from Home Depot, covered with flannel. You get at least the 3/4" size & you can cut it easily to whatever size you like. Then she just wrapped it in flannel & taped the flannel on the back with either package tape or duct tape! She uses one that was about 3' X 4' (? guessing now, she was up on the stage! lol) when she teaches classes. She has big ones on her walls at home...and also reminded us that if we are putting them up on the wall at home, to be sure to use nails with heads on them - or else they will slide right off of the nails when you have your blocks on them! LOL