If a slime block is placed in a slime chunk, particles will fall from it.

The mechanic itself is simple. Simply place a slime block on any block inside a chunk, if small green or slime particles start dropping from it (kind of like how full bee nests drop honey particles, if the slime block was floating, or like how crying obsidian drops purple particles) then that chunk would be a slime chunk.

I imagine players running from chunk to chunk, placing the slime block in each one to find the slime chunks, it would be cool!