I thought about doing that a couple years ago, but i was gonna use cardboard to make the shape of a dirt mound and coat that with glue then dirt. Never got around to it tho. I think the towel idea is good, but i think the cardboard one has a couple advantages that i'd prefer. the towel has one advantage i can think of, but not enough to go that route. I really need to do this because every year i dig some dirt from the side of the house for the mounds and the hole is getting rather big !

Not only that but cleanup is a pain. But finding time isn't easy with all the other more important things on the agenda.