At the end of the Underground River area is a location with a large number of Kelolon monsters. Use the "Fleeing enemies keep running" glitch to cause the Kelelons to run until they all run into the invisible wall that prevents them from falling off the edge. This may take a while as they slowly move sideways across the invisible wall. Eventually ten or more of them will get close enough for you to attack all of them at once. Make sure you keep your Stealth active this entire time or they will jump into the ground and hide, requiring you to start over again.