Impact

What part of the ball you contact at impact plays major influence on the initial direction of the ball.  The book 'In Search of the Perfect Golf Swing' published a study back in the 1970's that stated 75% of the initial direction of the ball was determined by the contact.  Their tests results were produced by high speed cameras.
Recently Trackman posted a study that up to 90% of the initial flight of the ball is determined by the club contact with the ball.
To produce the ideal impact, the left forearm and hand rotate together to contact the inside corner of the ball with the face still slightly open but in the process of squaring up.  This impact starts the ball slightly to the right of the target.
The right hand plays a supporting role in the impact.  As the left hand creates the hit, the right supports the contact.  If the right becomes too active, it can cause the clubface to contact the outside portion of the ball inside of the inside.