I might not light a fire in it super soon, but I had some spare time today and decided to at least get the box built.  Not far along, but I'm happy to share my journey.  I'm going to use my utility cart to wheel in and out of storage, seems useful for that so far.

The box is about 7.5 inches deep.  Maybe more than I need, but using excess I had on hand was nice.

I'm going to try to source some bricks if I can find some free ones before drilling a hole for the  tuyere.

Still scratching my head on substrate.  Digging a hole in my small yard might upset my spouse.

Also checking for safety - when I hear about black steel pipe as a safe tuyere material, is the below picture correct?  It comes with a protective black soft coating of some kind, I think I want to remove that before getting anywhere near heat, right?

Thanks to everyone for this website as a resource.  I would have been doing something much less fun while waiting for local classes to start up again (probably not until next year) to touch a hammer to hot steel if IFI didn't exist.

2 minutes ago, Peter R said:

Still scratching my head on substrate.  Digging a hole in my small yard might upset my spouse.

You're bending down to far if you scratched your head on the substrate. Been there done that, don't recommend it. Don't worry your spousal unit will let you fill it with dirt in her new planter. 

Box looks good. A couplle inches of mineral soi in the bottom will be more than enough heat shield for the wood.

Frosty The Lucky.

I too could not dig a hole in the yard. So I followed Charles Mark III. I used cheap unscented kitty litter. Works very well.

The pipe pictured is what you want, I think the coating is rust proof stuff, I have never removed it. Yep cheap kitty litter is usually bentonite clay.

The coating will burn off if heated. Don't breath the smoke and you should be good to go for future use.