Wolf portal fortress farm

ianxofour's fortress farm, the one where the mobs push each other through the portals. Tamed wolves stand around the spawning platform, the wither skeletons and blazes back away from them, and the crowd shoves whatever is in front into a nether portal. Everything arrives on the overworld side of the bridge, gets killed in one place, and comes back as skulls, bones, coal, blaze rods and gold. There is no spawnproofing puzzle and no complicated redstone, the wolves do the work. The video also shows a pack spawning upgrade that costs 690 more nether bricks and 624 buttons and lifts every number by about 15 percent.

Spawnproof everything inside the spawn radius. den1xlUnavailable lost three days to bad rates before finding a crimson forest nearby that was eating the mob cap.
Bring 14 wolves instead of 12 so you can breed replacements, and build in this order: slab rows first, wolves second, nether brick floor last, or the mobs overwhelm you mid build.
Drink invisibility before you step through the middle portal. Everything that went through ahead of you is standing on the other side.
nellyw8991 warns that the instruction is to stand on the south east chunk of a chunk intersection, not in the south east corner of a chunk.
On a vanilla server a chunk loader does not save you. Someone has to be near the overworld bridge or the mobs despawn on the way.
GoDamit1000 added a second spawning layer and parked a chicken in a boat in the portal to shove stuck mobs through, and got 194 skulls an hour out of it.