Have you ever watched mud dry? I can tell you it happens excruciatingly slowly. I know this because for ten days I have been monitoring the progress of a four-inch-thick, three-foot-diameter beehive-shaped shell as it transforms from a mixture of soil, sand, and water into a solid, heat-retaining, bread-baking wonder (I hope).
At last report, I had a hearth and a doorway arch. From there, progress was apace for a while. First I packed the spaces between the arch bricks with mud. The following morning, my sister and my niece helped me create the dome-shaped sand form.