Watch the dude in white tee and shoes right at the beginning. I know he's flipping but it's the same deal.
For the straight-up nollie version, shift your back foot so that the ball of your foot is in the center (width-wise). There is no big wind up, a big wind up will just throw you off balance most of the time. Kinda face the direction you are going and add a small final rotation in the shoulders as you come out of the crouch and into the jump.
The most important part is the direction you throw your back knee in the pop. It's not straight up, it's up and towards the direction you are going. Just watch the dude's back knee, he throws it towards the top of the bank. Doing this got my Nollie FS 180s a whole lot less shitty.