The fabric needs to have a loopy texture so the little grabs on the snappi can hold onto it so flanelette is no good for snappis. You can use pins or the tie on snibs for flanelette.
Terry towelling or french terry would work. Even micro terry. They sell all of this stuff at SL.
You could get away with only using a terry type fabric on the areas the snappy needs to be but it would create a bit of work adding them on I would imagine.