If I remember correctly, one of the videos/handouts talks about situating the ball such that it’s aligned with your left ear. I tend to look at where the logo would be on a polo style shirt (over left breast) and play the ball there in my stance. This also ends up being about 1″ to 1.5″ inside of my left heel as well, if that’s an easier point of reference for you. This is, of course, only for “stock” iron shots. I tend to move the ball back in my stance a little when I’m wanting to flight it a little lower. I think it’s important to experiment with ball position a bit. Play around with it. Try to find what works best for you. Try not to overthink it too much. Good luck.