Based on Nick Collins’ flower-pot tandoor; this is a very cheap oven to build that is a big bigger (but heavier) than Nick’s. the top half isn’t insulated which may be a problem but it seems to cook fine.
DIY Tandoor Oven – Very Cheap
These kinds of ovens are used throughout the Middle East, India, Pakistan, and even parts of Central Asia and China. They can be large, permanent structures ensconced in a kitchen or outdoor area, or they can be smaller, portable ovens that can be carried from place to place.