1. Improve your upper body rotation (90º shoulder turn).
2. Learn how to keep your left arm straight as you swing back (widen your back swing arc).
3. Hinge your wrists w/o bending the left arm at the elbow (the power releaser).
Repeat this drill over and over very slowly. Be aware that your positions are mirroring what you see in the video. Slow repetitions will help you to memorize this move. Practice many times until you gradually incorporate these positions into your swing.