Ok then make a slime farm if you can find a slime chunk on your island, and have enough spawners ofc :P
oh. Hm... You could make a square surrounded with cactus, as slimes only travel in one direction, so the slimes would just keep walking into the cactus and killing themselves, and you set up some hoppers around the square to collect the slimeballs. That might work.
1.7 but 1.8 compatable kritt :P And yeah, that could. Being as my sword is OP I can kill them instantly if I wish