How to find slimes in 1.9.2 with no seeds

According to the Minecraft Wiki:

Spawning

---

Slimes spawn in the Overworld in specific chunks below layer 40 regardless of light levels. They can also spawn in swamp biomes between layers 50-70 in light levels of 7 or less.

Slimes will not spawn within 24 blocks (spherical) of any player, and will despawn over time if no player is within 32 blocks and instantly if no player is within 128 blocks.

Slimes require two vertical transparent blocks^[Verify] (e.g., air, signs, torches) to spawn in, with an opaque block underneath. The space they spawn in must also be clear of solid obstructions and liquids.^[Verify] Big slimes require a 3×2½×3 space to spawn, small slimes require a 3×2×3 space, and tiny slimes require a 1×2×1 space (or 1×1×1 if the upper block is not opaque).^[1]

Slime size is affected by regional difficulty: chances range from 33% for each size at low difficulty to 16% tiny, 33% small, and 50% big with higher difficulty.

Swamps

In swamps, slimes may spawn at night between the heights of 50 and 70 provided the light level is 7 or less. They spawn most often on a full moon, and never on a new moon.

More precisely, the game checks if the light level is equal to or less than a random integer (from 0 to 7), then if the fraction of the moon which is bright is greater than a random number (from 0 to 1). If these conditions are met and the altitude is acceptable, there is a 50% chance of spawning a slime.

"Slime chunks"

Slimes spawn throughout the world (except mushroom islands) below layer 40 regardless of light level, but only in certain chunks, 1 in 10 of all chunks. These "slime chunks" are determined pseudo-randomly by combining their chunk coordinates with the seed of the world:

Random rnd = new Random(seed + (long) (xPosition * xPosition * 0x4c1906) + (long) (xPosition * 0x5ac0db) + (long) (zPosition * zPosition) * 0x4307a7L + (long) (zPosition * 0x5f24f) ^ 0x3ad8025f); return rnd.nextInt(10) == 0;

That is, using the chunk coordinates to help generate a seed, a random number between 0 and 9 will be generated, and if that number is 0, the chunk will be able to spawn slimes. To convert world coordinates to chunk coordinates, divide by 16 and round down.

So your best bet will be to dig down in a swamp biome, and then create a few big rooms for slimes to spawn in.

If you have a hard time finding slimes go to a swamp biome. Its the biome slimes spawn. I think they can spawn other places too but im not sure. Hope this helps!

Go to a swamp biome, find the lowest open area you can, and build a roof. Leave at least 2 blocks high space and cover as much area as you can, then dig a cave for yourself and wait. Natural light lvl in the swamp is usually about 9, finding 7 is tough. So make a roof to block as much sun as you can and wait. Worked for me in about 10 minutes.