No tutorial out there, but its a pretty simple build till now.
In fact its just what you see on the pics: base cut to size, walls glued on, sand glued to base and the inner walls are painted using white acryl to get some texture on the smooth surface of the cardboard. The outer walls will be textured using an airdrying model clay. I will take some pictures when I do this later.
edit:
This is the next step: for a nice texture you have to take small balls of putty and plaster the wall, a wet fingertip will help to smoothe the surface a bit. (This is very time consuming...

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Till now I always used white clay, but I think this one is easier to prime, as you won't notice any missed parts later...
