I also wanted to create a large building as a center-piece for the board. I wanted something with a playable roof with some stairs. My older daughter drew the original design sketch, which I reworked into something practical, and we built it together on a day off from school.
We took some scrap foam and a box for the basic shape, and I made some buttresses out of pink foam.
I cut out some stairs freehand. I ran out of pink foam and had to use some of my scrap foam.
We put together an entry way from a spare box and my last scraps of foam.
We plastered the problem areas with spackle.
Then we painted like crazy. My younger daughter did about half of the painting, which turned out great. She is very neat when working with large areas.
And here it is in near-final form:
I still need to add some shadows and highlights, as well as doors, control panels, posters, and other finishing touches. I was thinking about making a sign in Aurebesh. I was thinking about making it an inn named "The Wretched Hive"