A clay pot. Tea candles. A safe surface.
I placed a muffin tin upside down and put the draining tray on it. 4 tea candles. Light the tea candles. Then I turned the clay pot upside down and sat it over the candles.
The heat started coming out the small drain hole. A temperature probe measured the heat. 275 degrees Fahrenheit. Once the clay was heated up, the temperature stayed around 225 degrees.
I lit the candles around 7:30 a.m. I left them burn until they were consumed. It was 3:00 p.m. before the last candle burnt out. There was a radiant heat from the clay pot.
There was plenty of draft. The air came in at the bottom and came out the top.