The hook is caused when the club face is looking to the left of the direction you are swinging
Advanced player looking to add more width on their backswing and improve their left arm position should try this neat little drill from Vijay and put a headcover under their right arm
There are two parts to the release, one is the arms turning over and the other is the body turning, we need both of these to release correctly but most of us tend to over emphasize one of them