I used 2 insulation sheets from Home Depot, each 4' x 4'. I had to remove about 2 1/2" from the top so it could fit comfortably in my 'studio.' I worked on my garage floor [covered in plastic to keep my work clean] and duct taped the 2 sheets together so I could fold them together to save room when not in the fully opened position. A friend helped me spray the insulation with permanent spray adhesive [from Office Max.] Then together we applied the batting to the sheets.
You could use flannel, felt, narrow wale corduroy, or batting. I like the insulation sheets because they are lightweight, affordable, and easy to pin into if the need arises.
Since I don't want the design wall to tilt or fall into the ceiling fan I put in 2 eye screws at a level I could easily reach, about 6"+, and put ribbon across the front of the design wall to keep it in place. I tied a bow at one end so I can easily remove the ribbon and fold/unfold the design wall as needed. When not in use it is in a folded position.