I am not a believer in keeping the rear foot flat. I believe it restricts hip rotation.
This drill will stop you from snatching the club in transition (getting quick), stop you from hanging back, reduce EE and help better hip rotation.
Use hip shift and rotation to pull the right heel off the ground to start the dowswning.
Now this drill is not exactly what happens, nor is it exactly what you want to do, but it has very positive affects.
It gives you feedback on how the body will feel when it shifts and unwinds in transition…which in turn will give you feedback on how the body should wind up in the backswing.
You know I am not a believer in the hips getting out in front. That is why this drill works. If/when you do this drill you spin out, or feel your arms are getting stuck, you are probably doing that when you swing.
Again, it is a feedback drill to teach you proper sequence. If it makes you do something bad, then the drill works as a diagnostic and helps you find a feel that moves you in the correct direction.