A proper urning backflip (otherwise known as an ultimate burning backflip) can only be performed if the excess paper is lit near to the roach, then held pointing upwards, so that the paper burns upwards, like a wick on a stick of dynamite, all the way up to the end (which should have been loosely twisted). at this point if your timing is perfect, you can twist the joint, point it downwards and begin to toke on it. if you have done it just right you will be able to spark the spliff from the original fire caused by the burning off paper.
you can see that then name burning back flip comes from 1) the backroll and 2) the motions the joint makes as you light/toke it. not only does this look cool but it is also a nicer smoke, as you have removed excess paper that you would have been inhaling
dude: "gnarly bro! you must be a professional stoner!"