To get a boost when you start gliding, simply put a Jumppad right next to teh Gliding Pad, so the overlap (as shown in the picture).
If you have done it correctly, you just have to walk right between them, so at the area where they overlap.
Then you should get doubled the altitude of a normal start.

Note: Its not working every time, so you may only get thrown into the air without a glider or you just get a normal start.