Keep the clubface square: press your hand against a wall
The instructor offers a feel for keeping the clubface square in the takeaway: imagine swinging your right hand back against a wall — you would never roll or open your hand, you'd keep it completely square. He relates the hand to the clubface, so the idea is to keep the face square rather than rolling it in the takeaway.
Channel: Danny Maude
Watch official source at 2:37