Find a mob spawner in a dungeon, mineshaft, or stronghold
Light up the surrounding area so only the spawner room is active
Clear the room around the spawner
Dig out a larger room around the spawner, about 9×9 or bigger
Make the floor level with the spawner
Place water streams to push mobs toward one collection point
Dig a drop chute or kill chamber where mobs will gather
Add signs, slabs, or trapdoors to control water flow if needed
Make the drop height enough to leave mobs low on health
Build a safe spot where you can stand and hit the mobs
Add a hopper and chest under the kill area to collect drops
Keep the area dark so the spawner keeps working
Stand close enough to activate the spawner
Kill the mobs manually for XP
Repair and expand the farm if mobs get stuck or stop flowing