Cabinets against a slanted ceiling

[Jsmola]

I'm trying to add some built ins cabs/shelves along a slanted ceiling line in a cape.  Can't seem to figure out how to handle the top of the cabs against the sloped ceiling. In fact dealing with the dormers has been pretty frustrating. I'd settle for custom shaped shelf instead of cabs, just need the visual hole filled.  Any ideas how to accomplish this?