Before building a slime farm, first decide whether to build it in a slime chunk or swamp biome. Every chunk that is generated in a world has a 10% chance of being a slime chunk. Within slime chunks, slimes can spawn when Y < 40. (Tip: There are sites that can map slime chunks for you). This method requires an underground room to be dug out before the farm is constructed. Slime spawning in swamps can occur between Y=51 and Y=69. This method has the advantage of not requiring a dug-out room prior to building the farm, and the size of the farm is not limited, unlike the slime-chunk method.
|Chunks Mined||Probability of Finding at least 1 Slime Chunk (%)|
The first step in constructing either farm is the spawning place. In most farm designs, spawning platforms are created which spawn slimes that are then moved to a killing trap, usually a drowning trap to split larger slimes down and dispatch the smallest size. Spawning pads are usually constructed with a 2½-block gap using slabs, to allow all types of slimes to spawn. It is important to light the spawn platforms up, otherwise other hostile mobs can spawn too. It is also recommended to light the area in a 128-block radius around the farm, to keep the hostile mob cap as low as possible.
The second step in building a slime farm is transportation. In pre-1.8 traps, this is usually achieved by using 'canals' of water separated by signs. As slimes can swim in snapshot 14w06a and above, specific water placement is required in Java Edition 1.8 and above.
Separation and killing trap
The final step in building a slime farm is the separation and killing trap. To separate the different sizes down to the smallest, a drowning trap is usually used. The largest type of slime is split to the medium size, and medium to small. The slimes are then taken off to another trap to be killed, usually another drowning trap. For greater efficiency, the separation trap could be used as a killing trap as well, although this can be difficult in slime farm traps if the spawning room is too small.
Alternatively, a water stream carrying the slimes flowing into a cactus trap can be used. Hoppers around the base of the cacti then collect the drops. This has the advantage of killing all sizes of slimes without the need for separation. A downside of this method is that the cacti destroy around 20% of the slimeballs that are dropped.
A quick and lossless method for killing slimes is using magma blocks. Slimes can either be pushed there with a water stream, drawn there by iron golems, or allowed to roam off the side on their own. A hopper minecart track underneath the magma blocks can be used to collect the drops.
Item collection (optional)
To automatically collect the slimeballs produced by the farm, create a hole below the end of the trap. Place some hoppers (a 2×2 hole is recommended for greater efficiency) above double chests.
Mysticat's 1.15+ Easy Slime Farm 3-minute Tutorial
A very simple design that gets you enough slimeballs without being overkill.
Jioge's 1.8 Slime Grinder Tutorial
Many slime farms, especially those involving iron golems and the mechanic of slimes sinking into a water pit, were broken in 1.8 release of Minecraft. Jioge has the solution with this simple trap. Slimes are now able to swim upward and on a horizontal axis, so it is important to take note of how Jioge places the water in the drowning trap.
ilmango's 1.10+ Slime Farm (18,200 slimeballs/h)
This slime farm's design is quite different from most of the others. It uses fewer spawning pads, which, due to the way the slime spawning algorithm works, increases the spawning rates (see video for more details). The slimes are then lured off of the platforms using iron golems and killed by magma blocks.