Duplication glitch

So to start off, you need classic crafting off and to have pick block stitched on and to have two blocks of the thing. Like two diamonds. Then place one block on the floor and the other in your first inventory slot. Then look at the block and press pick block and the, for ps4, press r1. Then press square and craft it all out of blocks.

There you have it, but try not to abuse it as it would ruin gameplay for your and anyone else playing with you.