Heavily based on Gossamer's parametric Tardis.
I altered the doors to be bevelled for easier mold release and tweaked a few values here and there for better parametricity.
Then I subtracted from a block, and added holes for skewers to help alignment, tabs also to help alignment and to assist in mold release by percussion, and slots to hold string or zip-ties or rubber bands to hold the mold together during pouring.
UNTESTED, post pics if this works for you!
The two numbers in the STL filenames are 1) the 'H' parameter (height from base to top of door) and 2) the width of the entire STL.