At the end of the Underground River area should be a location with a large number of Kelolon monsters. Use the "Fleeing enemies keep running" glitch to cause the Kelelons to keep running until they all run into the invisible wall that prevents them from falling off the edge. This may take some time 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, forcing you to start over again.