What you need:
*A Keyboard
*A Functioning Brain
*A Pickaxe in BABBDI
What you do:
All you need to do is grab the pickaxe, go over the item you want to combine, pickaxe the ground directly under the item, and grab said item while still in the ground. Whenever you let go, you will now have both items in your hand. You can stack this as much as you want.
Have FUN!