[MR] IRORI question

[Eric J. Campbell]

If you don't know what an irori is it's a japanese open hearth.

As far as I have been able to learn irori are period.  I am investigating
building a portable irori for events much along the lines of
http://www.mars.sphere.ne.jp/daigoro/sakuin/eigo/shrine.htm

I want to build a complete irori and jizaikagi
http://gojapan.about.com/library/photo/blculture_irori.htm

however when I am looking the metal firebox it apears as though there is
5-6 inches of sand in the bottom of it.

What I need to know is how deep does the sand need to be not only to
insulate but to also alow skewers to stay upright?

If anyone has the information for a wooden fire box that would be great.

The purpose of this will be to practice japanese hearth cooking at events
and at other times.

any good references would be appreciated.

Domo arigato
-Xavier de Lyon