Pulling the handle of the club down to the ball during the downswing will create a slice, initiate the downswing with your hips and left shoulder
Shanks occur in the one plane swing because your arms are too far out in front of your body so concentrate on bringing your hands in closer to your legs on the downswing.
Use your right forearm to turn as you go through while the left arm is folding in. Make sure to maintain an arc in your swing as this short swing still requires a rounded swing path.