Here are some files that will help you in this game.

125K.fmz - form•Z model file

125K.zpf - form•Z preferences file

t3.html - This file that makes your gallery entry readable on the web.

To get the design process rolling, here is an example idea that could be used to generate interlocking solid and void spaces. The image sequence illustrates how voids are cut from a solid to produce a series of hierarchical spaces. This is however by no means the only way that solid to void relationships can be formed, so take the example with a pinch of salt and explore your own ideas.