Unhook, get out of the foot straps, and rake the sail back like you are going into a tack. Keep your body weight forward.
Step in front of the mast and anchor the front foot. This will be your pivot point for the backwinding.
Throw the sail forward into the eye of the wind a step hard onto the front foot. Slide the front hand back on the boom just a little. This will provide you with more leverage.
Move the sail forward to get more of the sail exposed to the wind and to force the nose of the board into the other direction.
The board will now be facing the other direction. Extend your arms a bit and make them slightly rigid.
After getting backwinded, you tend to rake the sail back to the nose just a little bit so the center of effort is more to the rear of the board.
Find the sweet spot and maintain the stability of the rig. Your head turns slightly over shoulder looking in the direction you are sailing. This feels a bit odd at first.
Your front arm is angled across your body.
The foot of the sail is leaning against your shin.
Your hips are forward. Your rig will move slowly in the desired direction.
You control the sail by pushing in and out with the clew hand in addition to moving the sail forward to the nose or backward to the tail. All these movements are subtle. Learn to feather the sail.
Here we are. You can do this for a long time by learning to feel the wind and to be in the moment responding to the subtle changes of the wind and your rig. All connected; all in harmony. You have now entered the Zen of windsurfing.