how to create one in a breakfast nook

[wdwinder]

Hi All, new here. Just got Interior Design 9 as a gift. I have started modeling my home so I can try out different design ideas, naturally.

But I have a question about how to create one in a breakfast nook. Its the three sided kind of bump out deal. not a bay window, since walls go to floor and have individual windows in them, but the ceiling height in the nook is lower than the rest. I tried soffits, one on each face, but I how to I cut them off to make a flat face flush with the main room wall? I tried an invisible wall and lowered ceiling in the little bump out 'room' but there is no veritcal face to it. Do I need an interior wall that starts way up above the floor?

Lastly, how do you make all those cool stand alone soffit things above? I thought they had to attach to walls?

thanks
Dave