I use a flannel sheet and it works fine. I am going to put some button holes on it though and get the hooks for my next quilting retreat.
I also have a felt one at home. I used the cheap felt you purchase on the bolt from Joanns. It holds small pieces fine but once you start putting your blocks together I need help with pins. The kitties and the air from the air conditioner vent don't help either. I think if I would have purchased the more expensive felt, it would work better also but wanted to go cheap.