Using subdivisions and then pushing the faces in to create a room at the top of the pyramid has the nice effect of leaving the normals facing outwards, which means when exporting / rendering there are no issues.
Are there any alternatives to this method?. What is the standard convention in blender or 3D modeling in general to create interior spaces in models? I tried deleting some of the outer faces and making new faces using the verticies on the inside, but that didn’t work so well, since the normals for the inner and outer faces seem to be linked.