Hi Lisa! I'm glad to help with your design wall project. I found that the easiest thing was to buy a twin bed size, flat white flannel sheet. If I recall correctly, I was able to purchase it (not in a bed set) through JC Penney on-line. The sheet fits around a single sheet of insulation that came from Home Depot or any home improvement store. It'll be either pink or blue (Corning or Dow brand) and is about 4' X 8'. I just wrapped the bed sheet around it and used duct tape on the back to hold it in place. You can leave it like that to move around, or hang it up.
My basement sewing area is unfinished, so I hung my design on a concrete block wall. I simply nailed two finishing nails into the wood at the top of the concrete blocks, then used old-fashioned curtain hooks--poked into the insulation--that then hung on the nails. Not fancy at all, but it works. I like the insulation because if I want, I can also pin into it.
In the photo you can see a new design I'm working on, and the paper design and strips pinned into the insulation. Linda