Today, I need to finish installing the first-floor bay so I can start on the porch. Although this bay is designed to be removable, I'm making it permanent. There's plenty of space in the back of the dollhouse for furniture around this area. The bay is removable to allow a view of the staircase from the front, but I can achieve that through the windows. Ultimately, it's up to you whether you want it removable based on your plans for the dollhouse.
As with the kitchen bay, I wallpapered all visible areas by patching together pieces. Once the bay is in place, you won't notice this. I also wallpapered the area visible through the windows to ensure no raw wood is exposed. Later, when I work on the interior, I plan to buy fabric to upholster the window seat, so I'm leaving it as raw wood for now.
I glued on the trim for the interior bay opening. Before gluing the bay in place, make sure to attach the windows first. It will be very difficult to do this from inside once it's installed. The interior sill is meant to sit like the exterior window sills, but for this bay, I placed it flat like bottom trim instead. This approach covers a larger area and finishes off the bottom of the window better. I might use this method for the other interior windows as well. Alternatively, you can install the sills as intended and then add extra trim underneath for a similar effect. Assembling and installing this bay was not difficult. Just clamp it well and let it dry overnight.