Do this in the challenge 'Survive the Doggobots Onslaught!' on hard (Raining Seamines)
Easiest way I found to do this is stay up top on top of the single platform. If you press down and X you kind of spring up so do this mixed with double jump to dodge enemies and mines. If you get hit try to collect your piece of body. When you get near 10 seconds try and let an enemy hit you once and then again before times runs out.
You need to have 2 body pieces missing when the challenge completes.