We learned a lot doing floor trench drains. The drains come pre-casted in concrete which in theory make them easy to in install. Either set them onto rebar or specially designed seats into the dirt, or hang them. We opted to hang the trench drain.
Unfortunately the floor in our building is not quite level so over multiple days we made small adjustments to get it just right. Then locked it into placed in a few select locations using some fence post mix.
The chair system is probably easier, but you would still have to weigh the drain down so it doesn't float when pouring concrete.