I'm on a skyblock server and want to find a slime chunk. I don't have access to the seed, so I need to search. What I did was go down to level 35 and make a platform 8 wide and 100 long. The center line of the platform is a chunk boundary. The platform has at least a 4 x 4 area in 16 different chunks, and most are 4 x 16.
And... no slimes. Am I just unlucky? Or is my platform design somehow suppressing slime spawns? Is it to narrow? How wide does it have to be? Would even a one wide platform allow small slimes to spawn?
If you go to chunkbase and just input a random seed you can see that while slime chunks are frequent, there is not much consistency. I.e. you can easily have gaps as big as 7x7 chunks. I would make a platform at least 8x8 chunks (128 x 128 blocks)