Find a dark area where mobs can spawn
Build a large enclosed spawning room high above the ground or over an ocean
Use solid blocks to make the floor and walls
Add a roof to block all light
Place water channels to push mobs toward a central drop point
Build a hole or chute for mobs to fall through
Make the drop tall enough to damage mobs but not always kill them
Add a killing area at the bottom
Place hoppers under the killing area
Connect hoppers to chests for loot collection
Light up nearby caves and surfaces to increase spawn rates
AFK near the farm to keep mobs spawning
Test the farm and seal any light leaks
Expand the spawning platforms for more mob spawns