I made one like the Jamie / Jimmy idea last year. This:
Conclude need higher temperature so either more fuel or oxygen required.
was my problem. It just didn’t get hot and cooking a chicken was more like singing one corner and warming the rest up.
My theory was that the intake at the bottom was too big therefore lack of suction. e.g. purse your lips and suck in vs open your mouth wide and do the same. The resulting pressure of air hitting the wood / coals wasn’t enough to whip it into a frenzy. I also used half bricks for the base, filled in with sand. I wonder if that loses further suction, but don’t know.
The upside down plant pot has since cracked when just having a burn so it needs completely redoing but now I’m reluctant as the same could just happen again. But I want home-cooked kebabs and Naan…
Actually, maybe just more wood.