Jack quoted Jim Flick as saying holding the instep of your backfoot down keeps your right hip in check and I completely agree with that. Engaging the instep of the foot helps the hip stabilize in internal rotation (or in non-jibberish terms, working from your instep helps you pivot through the hip with sliding). In the same article Jack says ¦impact is a result of rolling your ankles back and forth which I also agree with. One drill I like using to teach this in is called Single Leg Hip Hinge with Rotation (seen below). What you will find in this drill is that as you hinge forward (first part of the drill) you need good balance throughout your foot, and as you rotation the hips open and closed (second part of the drill) you need to subtly roll your ankle very much in the same way you do in the golf swing to maintain control. If you have trouble with foot work, or sway/slide in your swing, I would suggest trying 5 repetitions on each side to build awareness of how the foot and hip relate to each other in rotation. Enjoy!