I think their setting are very weird.

The materials required by the bills are just put on the Circle. This way, the haulers can actually pick those materials back up. Hence the bill will never be able to finish.

Even if you manage to build a room and isolate the Circle from all haulers. There is only 1 mage working on the Circle at a time, while you can't order your mages to work on Circle in prior.

And large amount work required for the bill will as well making the mages collapse due to exhaustion