Assuming you are physically capable of creating external rotation in your trail arm, it is critical we learn to manage the right arm behind the ball before delivering a strike. Your right arm (and hand) are directly responsible for creating on plane swings with appropriate club path and attack angles.
Extra - if you cannot create external rotation in the trail arm, it is critical you have some trail sidebend to put the club closer to being "on plane"... hit fades, not slices and pull hooks.