Start by laying down on the ground with your arms right next to your body - like a push-up starting position but laying on the ground.
With an explosive push-up, pull your body up from the ground. Your legs should be pulled up and should get off the ground - like in a regular planche position.
But instead of stopping in a planche position, you should pull your legs up till you are standing on your hands only in a regular handstand position.
Try to get back to starting position as slowly as you can because you could hurt your legs if falling too fast.