April 12: I dug out the sod, and kind of leveled
the surface. I scrounged the stone (and what
Build 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 --
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)