One: Kitchen worktop, practice just balancing with one hand on it and your feet on the pedals, which is hard enough at first.
Two: Once you’re comfortable staying still on it, try rolling back and forward half a turn. Do it a hundred times, then swap sides. Keep doing that every day for a quite a few weeks.
Three: Launch yourself from one worktop to another. Try pedalling it around the house using the walls and floor for support.
Four: Find something like a pillar or tree somewhere flat and spacious. Try riding away from it in a straight line as far as you can. Rinse and repeat.
Five: Learn the three methods of cornering and how they all make it behave slightly differently: Swinging your shoulders and arms, pedalling harder on one side, and leaning for fast corners.
It took me six months on and off, and I still can’t freemount. After that long developing my balance though, I could miraculously track stand when I hadn’t been able to before.