Replying to Coaching

So my younger cousin is trying to learn park and he asked me to teach him some of the basics. so far he has 360 540 270 on and switch 3's and 5's he wants to learn a backflip but I don't know how to go about teaching him how to do it since I just watched a ot of videos and hucked it until I figured it out. he is in the same boat i'm in snce we dont have access to trampolines, pools, or water ramps. How should I go about teaching him in a manner that isn't totally stupid