Use fireplace cement comes in tan or black,good for 1100degs I fixed an ascoti, old freehand one made by peppino,digging the Dottle out they had made a an indention way below the draft hole I got a cartridge of Dap firestove cement an dabbed a little in the bottom, got the hair dryer and got a skin on it, loaded it up and started puffing,when it went down to the ash I left it in and loaded it up again, cures with heat,when that smoke finished I left the ash in and let it sit. Good smoker now bottom slightly below the draft hole,by the way this cement is only silicate, what they make glass with. Worked fine Tbradsim the old cajun