What I have started to use are 3 100%woolen sweaters bought from Value Village (goodwill).xxlarge size felted them in hot water wash and hot dryer and they work wonderful. stacked them up its close to 1" high. my seams are so flat! the top sweater loves to pick up loose threads.. Been thinking about covering them with muslin but haven't done that yet. the sticky lint roller works good enough to pick up the loose threads.