As above I can't get the seat post clamp sufficiently tight enough, I put my right foot on the pedal to start a downstroke, which also forces the seat into my crotch which then lifts you off the floor the seat twists to the left.
The OS of the seat stem is 24.8mm & having difficulty finding one, I will look at removing the quick release part & replacing with a bolt, just haven't found time yet.
I live opposite an old barn with a level concrete floor. I found that starting off with my arms touching something either side worked well. Start with a foot at about 2 o'clock, but most importantly pick a spot on the wall at the other end of the barn and focus on it, then ride towards it.
After about 2 hours I could ride the length of the barn.
After a couple of days I could come to a halt, a day or so later I could turn around and ride back.
It is really good fun, and bizarrely I found it easier than learning to ride rollers!