Will try it. It's kinda what we had in mind. I was going to build a frame, but we have plenty of old star pickets that will do nicely.
I've built a few & settled on an open kiln made out of corrugated iron.
I've found just getting charcoal in the ground to be super beneficial. My priorities are getting the most charcoal with as minimal time/effort as possible. I've no shortage of branches & debris to burn here.
Basically cut 5 or 6 lengths of corrugated iron about 1.2m long. Bolt then together top and bottom with some overlap, making sure 1 side is even (it will be sitting on this end). You need it to be about 4.5m long because you'll fold it up into a 1m² square. Wire some old star pickets to the top to provide structural support & you're done.
nostr:nevent1qqs9hd9gu75dhjkpxrk9rhhk7rphsd4uwruq79pm6f2sl4n3rns7vyq28mqpu
Discussion
It's robust enough to hold big branches/small trees while burning. When you're done it collapses on itself into a 2m X 1.2m sheet.
The heat produced in the centre is incredible. You can throw green branches in & it quickly vaporises/burns with little smoke.
The major downside is the water required to quench it at the end. It needs a lot of water (50-80L) & you need to hit it several times to be certain. If you have 1 hot spot left it will turn most of the charcoal to ash overnight.