1: Preparing the base

Foundation

Nothing makes you more happy than watching the cheese melt of a pizza in your own oven. Therefore it's recommended to have your oven door at a proper height to easily peek in. In general a height of about 1,50 m is sufficient. While looking around for materials to build a proper base to reach this height, I found out that choosing a proper location helped me a lot. :-D I could place my oven on a bank that already provided an elevation of about 1 meter.

Since there is no base construction, the oven rests directly on the ground. Therefore I decided to make a wooden base plate to prevent moisture from the ground climbing up into the oven. I found some suitable boards, though they measured only 95 x 33 cm. Making the main measures of the oven a tiny bit smaller than the preliminary design. The oven also has protrusion on the oven entrance. This could support a longer entrance with a chimney or just facilitate the pizza baking.

The whole base plate rests on 3 lines of bricks. The soil under the oven was very clayish and compacted so I decided to build directly on this soil without any sand, gravel, concrete or whatever other people might use for foundation. I'm kind of a rough worker, though I've learned that a proper start saves a lot of work. A sprit level is a big help in doing so.

Mixing the cob

Cob is a 2: 1 mixture of sand and clay. Making cob requires mixing sand and clay, such that every sand particle becomes coated by the smaller clay particles. Doing this requires some time and energy. Best do it with more people and some (life) music. 

For me it worked best to first put down a layer of sand and then add the clay manually (like mozarella on a pizza). Then I walked in circles till everything was spread out to the edges of the tarp. I pulled the tarp up from the sides to heap it all up together and start over again. As soon as everything is nicely mixed you can the very sophisticated consistency check, described on the ClayOven website. 

For the insulating layers  straw has to be added to this mixture. I would suggest that it's the easiest to add straw AFTER mixing the cob. Just add as much straw as possible while keeping the mixture still sticky enough to build with it. I know this sounds a bit vague, but just try and get some feeling for it. For me mixing worked best by making a lasagna with layers of cob and straw and again, walking around in circles. 

Best keep some shoes next to the tarp as well, so you can leave your wellies dirty when you have to interrupt your work for a toilet visit, changing the music, lunch or whatever reason. Mixing the cob for the base layers takes about an hour.

First insulating layer

The picture below shows how I've tried to fill as much space as possible with bottles. Even some small jars are added. The bottles overlapping the protrusion also act as extra support for this part. The bottles are again covered with about 2 centimeters of cob with straw.

Bottom of the pizza oven

The next layer of only cob becomes the bottom of the eventual pizza oven. I just emptied a few buckets of cob and shaped this into a layer of about 7 centimeters thick. Leaving about 7 centimeters around for the insulation. This resulted in the beautiful circular shape below. Since this will be the surface where you will bake your pizza on, it's recommended to level this again with a spirit level (so the molten cheese doesn't run off your pizza) and smoothen it out as even as possible with some water and a trowel.