I have 2 rolls (100 sq. ft.)of the ceramic fiber blanket that Forno Bravo sells. I'm thinking that should get me at least 3 layers. Then I'm planning a 3 inch layer of "vermicrete", plus a layer of waterproof stucco.
Next year, I intend to pretty it up with stone face on the bottom, a stucco finished enclosure on top, and filling the top with perlite. I figure that oughta do it!