Solution took from truetrophies.com, and written by Hi-Ed. All credits and thanks to him.
There are lots of opportunities to do this throughout the game. A quick way to get to one of them is to load up level 2 (Hallways). Early in that level you are trapped in a room and a bunch of skeletons spawn. Just wait for a three of four to spawn--hide behind Pontius' shield--and then jump on one, then immediately on another and then on a third. If you kill them before the trophy pops, loading up the level again and getting to that room doesn't take much time. I got it on my second try.