The two keys to executing a high, soft bunker shot are setting up with your upper body shifted toward the target and releasing the club so the clubhead passes ahead of your hands as it moves through the impact zone.
At address (1), notice my wide stance. (This shot requires the widest stance of any in the game.) My hands are slightly behind the clubhead, the club face is very open and, most important, my torso is tilted toward the target. This shot requires the full, normal backs wing you'd use when hitting a shot from the tee or the fairway. Avoid the common mistakes of shifting your weight to the right side and pushing the club to the outside of the standard swing path.
Remembering to maintain your weight shift toward the target, contact the sand right behind the ball while accelerating the clubhead with lots of speed through the impact zone and releasing the club. This motion feels like throwing an underhand Softball pitch. Just after impact (2), the club face should be parallel to the ground—imagine balancing a wine glass on the face—and all of your weight should be over your left leg.