Like its big brother, the 10 inch Bay Window, this was designed to fit a specific room box, in this case the Half Scale Window Room Box. This version is approx. 5" tall.
Note the open rectangular area on the back of the bay window's "back wall": that's to let you view into the room (through the window already cut in the Half Scale Window Room Box or any other small shrine you attach the bay window to). Or you can omit this feature and just glue the bay window onto a solid wall.
It has a solid bottom and two extra tabbed piece that glue inside to make a bottom for the window and the top. You can glue the tabbed "shelves" in at any height. It also has an extra solid top piece you can add for extra strength or the ability to decorate the top and add it onto the bay window unit later.
Cut from lightweight chipboard. Assembly is required, but it's super easy as the windows and tabs are pre-cut (and the folds are scored).