Doing an ollie into a nose manual is pretty much a basic street trick today. Basic, but when done well, impressive. Fletcher does them well.
Obviously you need to have a good strong Ollie to do this. Being able to do the manual on flat ground would also be good.
Also, you don't have to start on boxes quite this high. Something curb-height would be a good place to start.
Fletcher approaches the box at medium speed, ready to ollie. His front foot looks like it is a bit further toward the nose than a typical ollie -- so he'll be in position for the nose manual.
As he ollies, notice that his body is moving more forward over the board, getting his center of gravity in the right position.
He levels the board out a couple of inches higher than the surface of the box, with his front foot prepared to apply pressure to the nose. He's spotting where he'll land.
Fletcher touches down in a nose manual, arms extended so he can adjust his balance.
As he rides through the manual, he stays calm, making little balance adjustments to keep the rear wheels up without going over the nose.
As he comes closer to the end of the box, he begins to shift his weight...
...and as the front wheels are leaving the box he un-weights his front foot. This keeps his body weight from just pushing the front wheels down. With a little more skill you could snap a little nollie off the end.
He lands perfectly, with great style. Nice job again, punk.