On Saturday, Jack and I spent the day finishing fourth wall which contains the box window.
Two boxes were built: a top and a bottom. Both were built with 2x6s on the three exterior sides and a 2x4 on the interior side. The floor and roof of the box window will rest onto of the 2x4. We added the first piece of insulation to the floor and roof of the box window. Next, we screwed 2x4 frame that was prebuilt, using the specified window rough opening, onto the Top box. We were able to then place it between the wall studs, level it, and add screws to hold. Lastly, we the Bottom box in place, screwed the pre-built window box on the appropriate edge, then leveled the rest of the box between the studs and screwed it in place. The process of
building the window box was relatively easy. Additionally, I will need to add some nailing piece in obvious places where the T&G will be installed. The box window extends only 12" beyond the wall. I've decided to expand the width of the overall box window to about 48" to (1) add additional insulation and (2) enhance the look.
A box window adds depth inside and creates character outside. A lot of work for aesthetics, but I think it is worth it. I also must add the box window necessitated some on-the-fly design.