Here's what I did but to each his own. I have a mixture of MTH and Ameri=Town.
I cut a piece of 1/4 ply the same demensions as the Ameri-Town roof section.
I centered it on a piece of 1/2 plywood and nailed it in place about 3 inches back from the front edge so I'd have a side walk(the side walk from the kit goes in the junk bin) . Then I painted it with Val-Spar Light textured paint in sandstone color.
On each of the walls down at the bottom I drill 2 holes with a 3/32 drill bit. I set the wall against the 1/4 ply and nail it on with an N scale track nail . I don't drive the nail all the way in at this time. This allows me to run glue down all 4 sides with the bottoms in place.
Next I wrap a small bungee cord(Wal-Mart) around the building to draw the walls together. Then I use a small nail set to drive the nails all the way in. Believe me the nails don't show and you can handle the building a lot easier.
Another thing is , we all know how the walls of the Ameri-Towns tend to bow outward from the middle? well with the bottom set in place if you put 2 or 3 bungees in place on that building I guarantee you it'll take the bow out.
David