Simple Day one iron farm

A single module iron farm with three villagers on beds and a zombie in a boat. Golems spawn on a small platform, water pushes them into a hole, and they fall about 14 blocks onto campfires with the collection below. It is cheap enough to build on the first day and takes about an hour. Java only.

• Orientation matters. The hole and the water that pushes the golem into it go to the northwest, and several builders lost time getting this wrong.
• Nothing may sit higher than the spawning platform within 8 blocks of the villagers, no other villagers within 10 blocks, and no other iron golem within 16 blocks. Breaking any of the three is the usual reason rates are low or zero.
• Roof the zombie with slabs and extend the roof past the boat. Otherwise golems spawn on the boat or on the roof itself.
• If the villagers stop sleeping the farm stops. Block their view of the zombie for a moment, either with a trapdoor flipped down at night or a solid block in front of them.
• The zombie needs no name tag. A zombie sitting in a boat does not despawn.
• It does not run while you are away, so put it in the spawn chunks or use a chunk loader. Adding more villagers does not raise the rate, and swapping the campfires for lava makes no difference either.