DISCLAIMER: I have not yet learned how to do the mulitverse laying dive or whatever it's called.
also, I don't think this is entirely true. but it did work 100% of the time for me

First things first, we need to get into the dive
but the dive has to have miles facing away from the camera
it doesnt work if he is facing towards it, and instead the game initiates other dive tricks like the torpedo

then you press T, and press S
if you press A or D, you get the freeze dive

The easiest way for miles to jump backwards is if you hold shift while running off of a building
but you can also sometimes end up backwards after a swing.