Cheap no redstone iron farm

A starter iron farm for three villagers and one zombie, built from cheap materials with no redstone. The zombie sits in a boat where the villagers can see him and the golems drop into lava over the hoppers. The whole tutorial runs three minutes. Java only.

• Build at least 50 to 120 blocks from the nearest village. The creator gives both figures in different replies, so take the larger one.
• If the iron sits in the hopper instead of reaching the chest, the hoppers are not pointing into the chest.
• Put the villagers in place before the zombie, and do not open the trapdoor too early.
• One builder ran several of these about 20 blocks apart with no problem.