Minecraft wiki entry for Witch_farming, associated text: Once the farm is closed up you need to figure out where to set your AFK room. This is to ensure the highest amount of spawns and drops from the Witches without having to clear out a perimeter. This can be best found by finding the block above the upside down stairs and recording the Y value using the F3 Debug screen and looking at the coordinates of the "looking at block" space, when you hover over the block in question. If you are using the Tube style grinder, The hopper itself is the target you need to find the Y value coordinates. Finally add 128 to that Y value and create an accessible AFK room at that exact resulting Y coordinate number. For best results it is better to put your AFK hut in the middle of your farm so the spawning circle will be most effective at that farm.