http://chunkbase.com/apps/slime-finder then go to your desired coordinates and dig down to y 40
then dig out the 18th and 17th line ( so 16*16 you leave there ) dig down 3 spaces so the big ones van spawn . repeat until you hit bedrock .
wait until they fall to there dead.
if you need advice or if you have more question just send me your psn i'll add you .
Hey do you want to MC sometime?? My PSN is OfficialFBomb