The basic shape of the Gorktress has been made from foamcore. Read on to find out how I constructed it. 

I built the two towers first (wait, wrong game system). Then I cut slots into the side of both towers to slide the front walls and floor of the fort into. This works great because it supports the floor meaning I don't need struts.

I can easily fit 24 Arrer Boyz onto the platform, I have concerns that you might not be able to see them once I've built Gork's face and mounted it over the door. Maybe I'll cut the eyes out so they can shoot through them. Next time, I'm cladding the structure in wood.