Gather materials: building blocks, beds, villagers, workstations, iron golems, water buckets, lava bucket, signs or trapdoors, hoppers, chests, and slabs
Find a flat area and build the farm high above the ground or far from other villages
Build a spawning platform for iron golems using solid blocks
Add water channels to push iron golems toward a kill chamber
Place lava above the collection area to kill iron golems
Put hoppers under the kill chamber and connect them to chests
Build a villager holding area near the spawning platform
Place at least 3 villagers in the holding area
Place at least 3 beds for the villagers
Give each villager a workstation
Make sure the villagers can sleep and work
Add a zombie or other scare source where villagers can see it safely
Keep the zombie contained so it cannot reach the villagers
Light up the area to prevent other hostile mob spawns
Make sure no other beds or workstations are nearby
Test the farm by waiting for iron golems to spawn
Collect iron and poppies from the chests
Keep the farm loaded while you use it