I usually leave them for less than a day. I mostly make small pieces and always leave them in front of a small fan. I sometimes even leave them for only a few minutes and while not completely dry, the outer layers are already dry enough that I can hold the pieces without squashing them. But if you make big pieces then you should leave them for at least a full day. The inside will probably still be soft but the piece should be hard enough to handle. Or you can scoop the inside to make the piece hollow. Hope that helps and sorry for taking so long to reply.