Now all you have to do is to enter the trick with forwards momentum. I usually just take a quick step into it, like I would for gymnast type Aerials. Just approach this like you did for the Aerial Webster.
Try not to reach forward too much or else it'll kill your height.
Take off with your upper body at least parallel to the ground and not lower. Again, that will kill your height. Really good websters take off almost upright.
Your center of gravity should be right above your jumping foot or even slightly behind. Look at my hips before I takeoff. They are slightly behind my jumping foot before I takeoff. This makes it possible to push them upwards into the flip. If my hips were in front of my foot before takeoff it would push them forward instead of upwards, resulting in too much travel and less height.