In the mid 90’s I used to race at a weekend supercoss / speedway meeting in the Munich Olympic-halle ( the massive indoor velodrome stadium next to the main Olympic stadium.) 8-10,000 people watching. The speedway was on late afternoon / early evening, the floor was boarded over with wood and we were all supplied with Metzeler road tyres … they sponsored the event, lights / loud music/ lasers the lot.
For the evening event they wheeled in all the jumps / berms etc made out of wood for the track set up ( it took about 1/2 hour). The meeting was just as you’d expect with the riders disappearing into the stands under the seating, racing around corridors and appearing on the other side of the stadium. Brilliant mental stuff.
It was great fun, ( paid well), there was no expensive temporary track to be installed and apparently the supercross berms / jumps could be used at other events.
it’s not rocket science.