I've been practizing grey's its good here's how I think it goes.
1.start with your weight on the left foot!

2.right heel up!

3. Push into the ground with the left foot!

4.fall unto the rear leg kicking the heel out violently right hip points towards your opponent!

5. Pull left shoulder back as hard as you can!

6.Right shoulder should be slanted toward the floor.
It's a hard punch that takes your head off the line. What I like about this punch is that I can start with my weight balanced.