When I build a wheel, I have two old forks, one 135mm and the other 100mm. I clamp the appropriate one to my desk. Tjen I tape a piece of cardboard to the fork, marked where the rim needs to end up, and adjust spokes til it happens.
For truing a wheel, just flip the bike upside down. The zip ties in the video would work. I usually tape something to a chain stay. I can do better than what they did in the video,