You gotta go pretty fast to start, the easiest way to learn is go over a roller/knuckle pretty fast, sit back on your skis, put your left hand down (assuming you're spinning left, if you're spinning right, put your right hand down), just as the knuckle approaches start a slight carving turn, then as you get the the knuckle pop and drag your hand on the ground, if you wanna do a 1 just look back for the landing, if you wanna do a 3 just keep spinning and at 1 put both hands down and kinda push off the ground but keep looking around, same for 5 - just keep spinning, but you need to carve a bit harder and go a bit faster.
After you get that down you'll eventually be able to do it without sitting back on your skis, but just by popping as you get the the edge of the knuckle/roller.
