In our last POTD (see here), we shared an image of a ceramic kiln under construction at a potter's home workshop in Jabah, Palestine. As the upper courses of the cylindrical kiln are yet undone, one can capture a clear view to the firebox from above. The firebox is stoked with fuel through a the exterior wall, so no door to that box is visible. Instead what we see are windows that allow the heat/smoke from the firebox to fill the chamber where bone-dry vessels will be stacked for firing. The flipped five-gallon bucket communicates a sense of scale.
Materials have changed, but this arrangement of a vertical kiln is at least as old as the Roman period in Israel-Palestine.
If a good thing works, why mess with it?!