It was a real hassle getting it put back together because the walls had been furred out a couple of inches. We discovered when we demo'd the room that the lower part of the wall protruded out a couple of inches further than the area around and above the windows. To make the wall be on one plane, we furred out the portion above the windows as well. However, that meant a bunch of changes had to be done with the woodwork before it could be installed again.
Tragically, when we thought we could replace the vent pipe, we removed the original stool/window sill. So, first thing they had to do was to replace it. It was a pain to cut the new piece of wood around all the existing framing.
Then they actually ended up adding a small box within the window area to extend out the wood to the plane of the wall.Then they added the crown. The wide piece of wood was actually a nice piece of wood we planed that was originally removed from our kitchen. It has a nice grain.
Then they added vertical pieces to cover the gaps. The wood we used was mostly all salvaged from our earlier remodel and a few pieces from the salvaged douglas fir we bought a couple years ago. I believe one of the pieces was actually from the shelf that was formerly in this room.