Minecraft wiki entry for Door-based_iron_golem_farming, associated text: This is a single village iron farm designed by GruvaGuy in 1.9 using Golem spawn mechanics to achieve a 100% efficient iron farm. Very different to most designs and can be placed flush on the ground without any digging required. Though this is as efficient as possible it is also expensive in resources. The mechanics show in the video can be applied to most other iron farms.