Instructions
Go to the entrance plaza in the 72-hour game mode. This is the mall entrance at the game's introduction.
Get attacked until you have one health square.
Run into the camping store with the tent on the first floor and get on the bike. Use the bike to get to the second floor.
Ride full speed into the railing until you go flying off the bike and land on the lower level.
Go back upstairs and use the bike to fly off the railing a second time. Hit the ground running to enable the glitch.