Find slime chunks using a slime chunk finder or seed map
Dig out a large area in a slime chunk below Y=40
Explore swamp biomes at night
Look for slimes in swamp biomes during a full moon
Go to mangrove swamp areas if available
Search underground caves in slime chunks
Use a slime farm in a slime chunk
Check for slimes in specific chunks by marking chunk borders
Increase spawning space by lighting up nearby caves
Wait far enough away for slimes to spawn in the area