Being aware of the back of your left hand is very important. Lee Trevino said that the back of your left hand mirrors the clubface. So, if the back of your left hand is moving stright down the target line through impact, so is your clubface. At impact, Ben Hogan felt that the back of his left hand was actually bowed slightly towards the target. Byron Nelson focussed on his left hand moving through impact towards the target through impact as well.
It isn't a hard concept to grasp for golfers. The problem is that most right-handed players are naturally more inclined to want to hit with their stronger right hand. And that's not a problem as long as that left hand and arm keeps moving through impact and isn't over-powered by the right hand.
Golf is a two-handed game. But the swing should be a two-handed backhand. If your ballstriking isn't where you want it to be, try focussing on the back of your left hand at impact. It should be facing the target line. Just rear back and backhand that ball. Try it; you'll like it.