Either it's impossible, or I'm being dense, but how do I break a stack of objects in to smaller stacks?
Drop a stack on a crafting item slot - open (for example), the forge and then drop the stack on a slot. The first time an item is placed in a crafting slot it will only drop one item. The second time, it will drop the rest of the stack. This way, you can make a stack of 10 into a stack of 1 and 9. Repeat as necessary.