not found by me.
1. Make a Dispenser and put anything stackable into it.
2. Highlight it with your cursor.(DON'T PRESS A).
3. Get someone else to destroy the Dispenser.
4. Move the duped item into your inventory.
5. Go to a crate or chest and put the duped item in there one by one.(it will say take half at first but then just hold X).
6. Have fun.
NOTE: YOU CANNOT PLACE THE GLITCHED ITEM DOWN. IF YOU DROP IT, ONLY YOU CAN PICK IT UP.