LOL this reminds me of when I was a kid and me and a friend made a sort of underground furnace kiln in a hilside, which was lined with bricks we got off a site, and we used a hollow steel section gate post as a chimney. I still distinctly remember we used fresh wet clay (essex!) to seal the chimney to the chamber. Once it was going it fair roared and the chimney was dull red at the base......Of course a chimney doesnt have to be round (our gate post was rectangular)
You didnt say if your woodburner is for inside use or outside, just an ocasional one off or for regular use. But basically it needs to be as airtight as possible except for the inlet that leads air up through the grate. The flue will get almost as hot as the firebox so it needs to be substantially made......aluminum just isnt good enough (ok for gas fire flues but not woodburners) And ldealy one piece rather than joined sections, although if it has to run a long way if your in a building this can pose problems. I used a continuous length of twin wall stainless steel (the best) to get around this.
that i've cut a hole in and made into a door using hinges. How would I make the chimney (in the most basic way)? i.e without having to weld anything. 
