*excerpt from slab6.txt in the SLAB6 download found at http://advsys.net/ken/download.htm#slab6 *
Both SLABSPRI&SLAB6(D) support a simpler, uncompressed voxel format using the VOX file extension. Here's some C pseudocode that describes the format:
long xsiz, ysiz, zsiz; //Variable declarations
char voxel[xsiz][ysiz][zsiz];