The materials I've been using are:
PVA
Ice-cream sticks
Wooden skewers
Jenga blocks
MDF place mat
The platforms are made from ice-cream sticks with the rounded ends cut off. I've kept the ends rough and uneven because Orcs are idiots. Also, I'm lazy.
The central shaft of the tower is made of cheap counterfeit Jenga blocks which I've PVA'd together. At this point they're exposed, but I'm thinking of cladding them in more ice-cream sticks.
The ladders are made from an ice-cream stick with some one inch sections of wooden skewer glued to it for rungs.
The (mostly) finished product, assembled with PVA and mounted on an MDF
place mat I got from Spotlight. The base is too big for the model, so
I'm going to have to come up with some extra detail stuff to base it
with.
What's next?
I'm going to paint up some of the boards in an Orcish fashion, and apply some flock and whatnot to the base. I'll post some more photos when it's done.