Intro: Concrete Rocket Stove
Here's a rocket stove that will outlast you, but it's cheap and easy to make. But it takes sawing concrete... I used a 7" diamond blade on a circular saw for the occasion.
This takes three 8" x 8" x 8" blocks and a 8" x 16" x 1" slab for a base. One block needs the side sawed out so it can make the bend.
This is a true rocket stove, even though it is not insulated. To start it, you may need to throttle it by putting something on top to choke the exhaust air a bit. You might drop some dry dirt or sand down the chimney to insulate the base, but it's not needed.
It takes 1 1/4" standoffs on top for a pot so the flow is not restricted. Use rocks or sawed off pieces of the cutout.
The only thing that needs replacing is the coffee can in the inlet to raise the wood 1 1/2" for the air inlet.