I have read and seen lots of posts about going out and digging your own clay. Going to the beach and collecting sand. Then scavenging construction sights looking for old pieces of concrete. Looking for a free way to do this was not my goal I was more interested in finding consistent building materials.
I took the Home Depot and Lowes approach. I did do some scrounging for the base. I wanted an oven that would have a cooking surface about waste high. Something I could add a table or bench to if I liked the original product. This is what I did from the ground up.
I had my two teenage sons dig the foundation. Our frost level is 18 inches down we dug down about 20 inches. For the foundation we went to a local farm a friend of mine runs and collected broken pieces of concrete. There are more details on the post dedicated to the foundation.
For the base we spent several months camping in the hills around Boise and into Oregon collecting a variety of stones. I used the extra concrete chunks to fill the center and mortar to secure the stones. There is also a post on that as well.
The ring I used to contain the insulation I made out of concrete. The molds was made of wire and 1/8 inch press board that cost me $10.00 at Lowes. I cut it to fit the the concrete so we could level the top of the ring. It was not a consistant thickness but the top was level. I am unsure what if any effect this will have on the final outcome.
We filled the ring with beer bottles I got donated from the local tavern and I used fire clay mixed with water and used it to cover wood chips. I bought the clay at Potters Center in Boise (http://www.potterscenter.com/) for $25.00 for 100 lbs. For the entire oven I ended up 400 lbs give or take. I used a bale of pine wood shavings used as animal bedding I got from a local feed and seed for $10.00 or so. There is more on this in the lower insulation layer post.
For the cooking surface I created a 4 inch thick slab of a 1 to 1 sand and clay mixture. This created a thermal battery to store heat and a solid level to put the bricks on. I created a mold of dirt on the bricks in the form of the oven. The book said to use sand however I did not have any.
For the thermal dense layer of the dome I used a 2 to 1 sand clay mixture. This was not enough sand and cracked terribly. I ended up taking it apart and rebuilding it I then added more sand the 2nd time so it was closer to 3 to 1 mixture. It still cracked a little but not nearly as much. More on this in the dome construction post. I also reinforced my with chicken wire so if it it did crack it would not fall apart.
The outer insulation layer was similar to the lower level with a combination of wood shavings and clay water mixture called slip. I covered it with chicken wire so the final plaster layer would have something to stick to.
The outer layer was a 3 to 1 sand clay mixture with one part straw shavings for strength and 4 cups wheat past binder.