Pops said it right. You want the hind end of your critter higher than the front end when zipping it open. That moves the stomach away from the pelvis when you're starting the fielddressing cut. Once through the skin, abdominal muscles, and peritoneum at the pelvis, you use two fingers of the non-knife hand to lift the hide up from the guts and cut between them. Once that cut is made, front end up lets gravity help you pull the guts out of the cavity. These guys in the video were clearly working on the downhill end of their elk.