Spawn new object after last one is dragged away

I'm creating a 2D game with an inventory that users can choose objects from and then drag on an area where they can assemble the pieces in a variety of configurations. Rather than having each inventory slot hold only one object, I'd like each slot to hold a few copies of the same object, in other words when an object is dragged from a slot i'd like a new instance of it to pop up so the user can then drag another copy of the object if they choose to. How do I go about instantiating another copy of the object once it's dragged from the location?