Your shoulders create your swing line
Setting up with your shoulders open aiming left but with your feet in a square position.
If you set up like this to the ball this position will result in you taking your club back outside of the ball to target line and the club will be pointing left at the top of the backswing.
If you return back down to the ball on the same line from the outside this means that the clubface will be working across the ball leading to pulled shots to the left or if the clubhead is presented open slices off to the right.
Now try to set up with your shoulders and feet in a square position.
This orthodox position creates a good line in your backswing with the club in an on line position at the top (ie. parallel to the target line).
This should result in an on line inside attack on the ball with more shots hitting the target. It is important to remember that your shoulder line dictates the line of your swing.