Once I had the parts, and I had beveled the edges, I used a Right Clamp to assemble the basic tower.
I paid close attention to the belt rails and the clapboard siding in lining this up, since I could easily file the top and/or bottom of the tower if needed.
Using scale 1"x2" strip styrene, I started adding the belt rail and the corner trim,
I did the belt rail first, because that looked like it was done that way on the prototype, and then the corner trim. I use a piece longer than needed, glue it in place, then cut off the "handle."
I also test fit the stairs, gluing it on with Aleene's Tacky Glue, and I can easily remove it. I then tested the size on the layout, and it looks good.
Next I started the roof. Instead of looking up the math online, I started by drawing out the footprint on a piece of cardstock, allowing for a 1-scale-foot overhang. I then measured up a 2 scale foot line up past the center point, and cut out triangles to that point.
I thought those triangles looked like they would be too tall, so cut out a set of shorter triangles (about 1-scale-foot shorter). I used Aleene's again to glue them together and test.
I thought this looked too flat, so I split the difference between the short and tall triangles, and cut the final pieces out of .010" styrene.
Next up, adding details.