Single layer magma cream farm

Magma cubes spawn on a platform built above the nether roof in a basalt deltas biome. An iron golem lures them onto wither roses planted on soul sand, where they die, and a hopper minecart on a powered rail loop collects the magma cream and unloads it into chests at a dock. You stand AFK high above the platform.

It suits a player who already reaches the nether roof and has wither roses, or sweet berry bushes as a slower stand in. The whole spawning platform has to stand in the basalt deltas.

• Check that no block of the spawning platform sits over a soul sand valley. Skeletons spawn there and shoot the iron golem. Several builders on the linked block by block tutorial report it.
• When the minecart stops unloading, check the comparator and redstone torch at the dock. Builders on both videos report dock problems, one had left out the comparator.
• Building from the linked tutorial, set the minecart stop one block farther out or the cart gets stuck on the platform. 19 likes on that video.
• Without wither roses, sweet berry bushes on dirt, bone mealed, also kill the cubes at somewhat lower drops. Top comment on the linked tutorial, three builders confirm.