Ahaha, I just figured out the mount used in the unispin tutorial video, eg. at 1m10s. It looks like Jason puts his foot on the pedal at 6 o’clock, rolls the unicycle forward so that the pedal is at 9 o’clock, then jumps onto it. But that doesn’t work – I tried it! Rather, you gradually transfer your weight onto the lower pedal at the same time as rolling it from 6 to 9. The momentum of the “roll” acts to oppose the increasing weight you’re putting on the pedal, giving you time to get your body up and over the centre of the wheel before the weighted pedal finally defeats the momentum of the roll.
I’ve not mastered it yet. I can get onto the pedals, but usually end up in the dead 6-12 position. I once managed to roll into a seat-out hop though, so I can see where I’m going. Just more practise required. Seat-out hopping, which felt completely mental the first time I tried it, is starting to get better too.