I thought the same thing that I would want to wash the flannel but after 10 years, I never have done it. I use one of those sticky tape rollers to clean it off. I don't know why you would use batting. I used the 1" insulation board found at Home Depot. Used a dozen of safety pins and wove some wax string thru the pins so the flannel is snug & tight, kind of like a corset. I now have three of them and I don't know how I lived without them for as long as I did.