These pics are not very good, but you get the general idea. I used a header collector flange as a template and made my own with a lot of small bolts to hold, but the 3 that come with the flanges would have been sufficient if used with a gasket.
I also welded the pipe to the flanges. Also not necessary, but I have an overkill habit.
You make 2 vents, one for the door and one for the chimney to control air intake and temp.
This works very well. I made this in Iowa when visiting family. They also wanted a couple chickens and no one had a smoker.
Now it works very well to heat a small shed that my wife uses for gardening tasks.
When the bucket burns out, I just get a new one.
It took me all of 2 hours to make this, cutting, welding, and all. I could have done it in an hour if I had not cut my own flanges, and done the welding.