Prism99

I think the cotton flannel covered styrofoam (or other type of lightweight insulation board) is the easiest. You can probably duct tape two pieces together if one is not wide enough. I would cover with cotton flannel all the way around to the back and fasten in such a way (perhaps duct tape again?) that I could remove the cover once a year or so to wash it. This makes a lightweight design wall that is easily moved around. There are several different types of lightweight insulation boards at the big box stores. If planning on using duct tape, I would make sure that duct tape will stick to the kind you buy; not sure it sticks to styrofoam. A friend used a light green type of insulation board and her son-in-law put together a wooden frame for it. She just props it against the wall.

I have tried the curtain rod and command strip type of design wall before, in which I had Warm and Natural cotton batting hanging down. It didn't work well for me. Because it wasn't fastened on all sides, the batting had a tendency to wave. Plus because there was air behind it, it was sometimes difficult to get larger blocks to stick well. When you have foam insulation board behind, you have a solid surface to press against and you can even insert pins if necessary to get large blocks to stay in place. Small fabric pieces tend to stay in place, but large blocks get heavy enough that they tend to fall off.

Edit: My suggestion to make a removable and washable wall comes from having pets in the house. I found that Warm and Natural, when close to the floor, attracts startling amounts of pet hair over the course of a year.

Edit: Also, with my hanging Warm and Natural that had a tendency to wave, I found out that just walking past it quickly sent enough air currents to make it move and have blocks fall off.