Snow golem ring creeper farm

Creeper farm run by snow golems in fenced cages, with no cats and no redstone. Creepers spawn on a slab platform, golems penned in the corners knock them toward the middle with snowballs, and they drop onto soul campfires. Buttons on the ring in front of the fences stop creepers spawning right next to the golems, and trapdoors and slabs keep everything else out. Two chests take the gunpowder. The tutorial is two minutes long and filmed at half speed, which most builders manage but several complain about. Java, and Bedrock builders report creepers spawning slowly and spiders getting in.

The creator corrected his own list twice: you need one stack and 24 carpet, and you have to put buttons on the ring around the fences and torches on the roof, neither of which he mentions in the video.
A builder's corrected count: 8 snow blocks for 4 golems rather than 7, 12 buttons rather than 11, 21 fences rather than 17, and 13 stacks of trapdoors rather than 13 and a half.
Bring spare snow and carved pumpkins. Rain melts the golems, and they do not always end up in the cage you wanted.
Put more than one golem in each cage. They do not hit each other, and the whole design leans on how accurately they throw.
Place the roof and the trapdoors before the carpets. Carpet raises you a sixteenth of a block and throws off where the crosshair lands.
Build the AFK chamber at Y189 and close it in, so phantoms cannot reach you while you stand there.