April 12: I dug out the sod, and kind of leveled the
surface. I scrounged the stone (and what
Your Own Earth Oven
author Kiko Denzer in  
calls "urbanite" for fill) out of a vine-covered,
collapsed stone wall behind an old house. The
cinderblocks I used to make the "core" were in my
garden, left over from my hoop greenhouse
project. (See that
here. )  I filled the cinderblock
holes with broken bisque and pottery from my
studio. So far, total cost -- zero!
After filling the empty spaces under the future hearth with pot shards, I filled the holes with some sand the
groundhog excavated from his den into my garden.  Then I put an old broken silicon carbide kiln shelf on
top of it all and covered it with fine sand about an inch deep to lay the fire brick hearth..
Then I spent some money. I found a place downtown that sells
refractories, and bought 20 fire bricks for about $30, then picked up a
few bags of mason's sand at a couple bucks each.
To make the mortar, I dumped a bag of sand into a shallow plastic
storage box, and added wet clay.  It was a lot like a pie crust dough --
dry looking, a lot of little lumps that stuck together when squeezed.
Mostly sand! I used it to chink the spaces between my rocks, and fill the
gaps in the top.
My home page:
I spread fine sand over the old kiln shelf (and some broken bits I used
around the edges, packed in with my clay-sand mortar). Then I
nested the fire bricks down into the sand and leveled them.
I cut out a circle of newspaper 26 inches across and centered it on the
hearth. I measured the dome height I wanted (13 inches) and marked a
stick, and stuck it in the middle. The sand was to keep the paper from
blowing away. Next, I started piling wet sand on the paper and shaping it
into a dome..
Then I wrapped it in wet newspaper.

To see the next steps -- and the finished
inner dome --(it's page two of three)