Minecraft wiki entry for Wither_skeleton_farming, associated text: This design uses the ability to extend the nether brick platform of the farm area and spawn proofing the rest of the area, which allows more mobs to spawn in the area, allowing it to yield over 75 wither skulls per hour. It is designed on Bedrock Edition but can also be used on Java with it yielding about the same amount of drops, as long as you replace the trident killer with an entity cramming machine.