Fran,
I always use regular clay but you might be able to use my suggestion with air dry clay too. We sometimes use pieces of wallpaper to work on. We can wipe off if necessary and reuse. Sometimes I just give them a paper towel to work on. They also can write their name and room number on the paper towel until I can get their names on the clay later. I also use pieces of burlap, gives a nice texture. They are cut to about 15" x 20".