I use some wool coating yardage underneath a remnant of cotton drapery fabric that is densely woven like denim or canvas. The wool fabric is an old piece that I think is 100% melton. Once washed, it is very flat and dense. A double layer was stretched and stapled to the plywood, then I wrapped the upholstery around the board. The weight of the board holds the canvas in place really well, and I can remove it easily for washing. I use this board for dressmaking, too, so I like having the wool for steaming and shaping seams correctly.