Lava Farm (Dripstone)

This whole farm hinges on one specific interaction: a lava source sitting above a pointed dripstone stalactite slowly drips lava particles down through the point, and if there's a cauldron directly underneath, it fills up over time. Scoop a full cauldron with an empty bucket and you've got lava.

The build is tiny compared to almost anything else here. Lava source on top, one or more dripstone blocks hanging below it (chain them vertically for a slightly faster drip), open air for the fall, cauldron waiting at the bottom. No redstone, no spawn-proofing, no hoppers. You just walk by and fill buckets when the cauldron's ready.

Really the only choice you're making is how many drip points to run side by side, since each one only needs its own source and cauldron. Stacking a tall column with several separate pairs at different heights gets you more lava per trip than trying to speed up a single point, which has a soft ceiling on how much taller stalactites actually help.

Lava buckets are the most fuel-efficient item in the game, smelting up to 100 items per bucket against 8 for a piece of coal. A modest farm like this basically removes furnace fuel from your list of things to manage, and the source block never runs out since it's placed, not mined.

Worth remembering lava does more than fuel furnaces too. It's half the recipe for obsidian, and it shows up as a kill mechanism in a few of the mob farms further down this page, so a small always-on supply near your crafting setup tends to get used more than you'd expect.