I know that this post is a few years old. But, I just searched it a few weeks ago to learn how to do it myself and the Melarch response was right. But in truth the Tray Ceiling worked out as 6 separate ceilings:
1. The Upper Ceiling
2. The Lower Ceiling
3. The 4 (not 3) perimeter ceilings that are sloped. Each ceiling must be sketched separately.
I attached a draft rendering of it. That sloped ceiling of the tray in back needs to be tightened up a little...but you can see here. I just needed to get 3 tray ceilings in a floorplan and the assignment turned into a 2 story model...which I do not mind...I am gonna probably do the same amount of detail on the other 17 floorplans in the assignment.