You'd take a piece of float glass, from like a window and slump it
over a ceramic tube you made/found as a form.  Put it in the kiln and
let it soften and after its really gooy pull it out for a second and
use poles to roll the hanging edges together.  The maybe flip it so
the seam is on top and put it back in the kiln.

?

Is this at all how you would form a large diameter tube from found
resources?
What size kiln do glass workers usually have; what is the widest sheet
i might be able to work?
can it be anealed in the same kiln it was slumped in?