Fountains are cast the same way bird baths and any of my other leaf castings are made. The exception being that when casting them , I not only make them so that the tip of the leaf is tipped downward to allow for easier flow of water, but I also use the area where the stem of the leaf origininated as the portal to which the tubing from the pump enters that recycles water from your pond. The basic plumbing needed for the fountain assembly is incuded with the fountain and is very easy to assemble.
I do have an inventory of fountains cast, but unpainted. I prefer to paint them to customers' specific desires as ordered.