Whats an easy way to learn how to back flip on a snowboard

there is no easy way

just build your own jump make it a little steeper than usual but not to steep because you will hit ur head on the lip. just roll up to it normal speed maby just a little bit faster what ever feels comfortable. roll off the lip and turn 90 degrees and immediately throw your head back and then your body will flip and you dont have to worry about spinning back that 90 degrees because your body will naturally do it by its self.