Hank Haney on the Correct Wrist Position at the Top of Your Golf Swing
What you’re looking for is your left wrist being flat to your forearm. Ideally the club face would be squared to your wrist as well.
If it’s not that way, then you either have it too bowed at the top where the club tends to be closed and a little laid off to the left, or it’s too cupped at the top where the face is a little too open and this is a little more upright.