For this trick you need twin-tip skis. First practice on small jumps, or even a flat slope. Use your head and hips to start your spin as you would if you were jumping on flat ground without your skis, or even on a trampoline.
If you are going big, you can wait before you rotate, if you are not start your spin after you become airborne. You will be going backwards while still looking at the landing. Keep your eyes on the landing so you don’t over rotate. Make sure you center your weight for the landing. Touch down with your tips first, followed by your tails.
Doing these huge and with style is almost as good as doing a bigger spin with no style.