The high flop shot can be very scary for most players. That's because you have to commit to the shot. Speed throughout the hitting area is essential; swing too slow and you will hit the shot heavy, too fast and there is a chance to hit the shot thin.
Start by placing the ball forward in your stance, open the clubface and place your hands slightly behind the ball at address. Use a full wrist cock on your backswing, keeping your hands slightly behind the ball through impact.
Mastering this shot takes a lot of practice, so don't get discouraged; the more you practice it, the more proficient you will become at it.