I followed the instructions exactly as far as construction was concerned. So, we start off with gluing one long and one short wall together. I love these Rite-Way clamps for this purpose. The middle section of the walls are not held in place, so I used some metal weights to clamp that area.
(external link: Rite-Way Clamping System)
Next up is the floor. I used white glue for wood-to-wood joints, sparingly applying it with a toothpick. Again, metal weights are used as temporary clamps while the glue sets.
Since the second floor of this building has such large windows, and since I would like to put some interior detailing into the building, I decided to stain the floor with Minwax "Dark Walnut" stain. I tried to avoid applying stain to the glue surfaces. Note that the photo shows the building upside-down; I also stained the invisible bottom of the floor, to prevent it from warping.
I could then join the two assemblies. The key here to make sure that all the joints are straight and perpendicular. I am using some small plastic clothespins as light-pressure clamps for the delicate window joints, and the Rite-Way clamps for the major joints. The metal weights were used to hold the building in such a position so that the yellow clothespins wouldn't rest on the workbench and thus put the wrong pressure on the joints.
And here is the basic box construction. As you can see, the floor is clearly visible with these large window openings.
If you have done any kind of woodworking before, or built any wooden kits, you'll know that over time joints can come loose. Since the interior of the lower floor isn't visible, I decided to cut some 1/8" square wooden strips to reinforce the interior corners of the building. Also note that I painted the interior walls. This is because the exterior will be painted, so painting both sides avoids warping.
The second floor's interior is visible, but I still wanted to do that interior-corner bracing. I used some small strip wood to attempt to accomplish the same job.
To protect the stained floor from paint, I covered it with some masking tape. I then painted the interior walls with Polly Scale "Depot Buff".