A two plane swing requires you to start your downswing with a hip bump forward and then arms pulling down, which relies a lot on having good timing
We are looking to create a clubhead that is traveling down to hit the ball, so take your address position and straighten out your left knee, this will bring your hip back, move the shaft forward and straighten your left wrist
Practice making half swing with this pen drill to maintain a constant distance to the ball throughout the swing