Self designed, kinda. It’s very straight forward simple 3x3x7’ box with a vent at the bottom ground level in front and exhaust at the top of the back wall. Propane burner for heat. I built a few other styles from masonry before building this wood box. Marianski’s book “Meat Smoking and Smokehouse Design “ was a big part of my inspiration in the beginning, then a little internet searching later.Something to aspire to! Is that a self-designed smoke box or are plans available somewhere?