There are several positions from which to begin this skill.  The Lunge is one of the simplest.  Begin in a Lunge position, with one arm in front and the other to the side.  Shift the weight onto the ball of the front foot, and at the same time, close the arms so that both are now in front.  This initiates the turn, and the back foot pulls forward to Coupé position.  The body turns 180 degrees, with no bends at the hips or base knee, and lowers to a flat foot, with the other foot still in Coupé.