I built one of those a few years ago as well. Let me tell you, they get HOT. I stacked some concrete blocks around it about a foot and a half away from the sides of the barrel and used some old tin roofing for the top. Unfortunately, when you live in town people don't find it very appealing. After a visit from the local FD, I had to stop.
A note on safety: do not let anyone open the barrel for a good 8 hrs or so. If your barrel is sealed, that means the fuel inside is starved for oxygen so opening it can ignite it in a very violent manner if it isn't cooled down first.