Alright. Try these on a trampoline first for sure.
You have to practice these on a tramp A LOT before it becomes a natural movement. You have to take it step by step.
1. Pop. Make sure you get a good pop
2. Go to about 90 degrees (a little off axis), and then throw a backflip.
I know this doesn't sound like what the trick looks like in real life, but once the trick becomes natural on the trampoline, then all of these movements will look like a true flatspin. At first when you learn it, you have to break down these movements one by one and then once you understand the trick, it will become one fluid motion.
I haven't tried them on snow yet but I have them pretty much dialed on tramps so any day now when i grow some nuts i will try it.
for sure dude just have one trampoline session where all you throw is the flat spin then you will get really good at it. Remember to take it step by step at first and then after you understand it keep throwing it and you should be set bro.