A SAWDUST KILN is a method to replicatethe conditions of a traditional reduction firing without so much smoke, animal dung or skill.
(SAFETY NOTE : DO NOTHING STUPID OR DANGEROUS)
You need a closeable fireproof container.
This can be a dustbin (metal........),
an oil drum (empty......)
or a box made of bricks/breeze-blocks closely stacked together.
You can also try a pit in the ground but this encroaches onto pit firing.
The container should not be totally airtight - bang a few holes in the bin or drum.
You should make a lid which fits snugly.