Real life usually interrupts my thought process.
I started on the floor. Cast in hirst arts tiles. I glue them together face down to create a level surface. Then the back is reinforced with more glue and putty. When it is completely set I filled all gaps on the top surface.

Then I built up the walls. I edged the bottoms and sides with Hirst blocks and added rough panels to fill the walls. Windows were added in and shimmed into place using coffee stirrers. The walls were then capped and doors framed with popsicle sticks.
Gaps were then filled with more coffee stirrers.

When these had set I glued the entire surface of the wall and covered it with cheap clay kitty litter. Then super glue was dribbled over all the kitty litter to protect it with a hard acrylic surface and to bond it in place. This will give me a surface similar to flint nodules.

Now to finish up.
Hope you like.
Snitchy sends.