So there are 16 vacant spots, and 2 spots taken.
You may take a spot for gameplay and decorating, or take both in one part.
Or do what Lucasyecla99 did in Diligence (the level this is remaking)
https://docs.google.com/document/d/1TKb-fFiTdgIwrcHcH78NTHhakB49m935mZ2iDa8sQZI/edit?usp=sharing