Large gravel fills the spaces between chunks.
Smaller gravel covers the floor to a depth of 6 inches. I expect to add one to two inches of pea gravel, then perhaps a final layer of flagstone for the actual floor. This could change. The flagstone was donated by a neighbor.
March 2013 and the foundation is ready for cob.
One problem ... the land was no longer supplied with water. The ninety-three year old hand dug well had dried up during the exceptional drought conditions. The problem is now resolved and the solution will be a subject for a future post.