I came across this free, downloadable publication on how to build traditional clay ovens – it will come in handy when we finally decide to build one for the company! Plus, there are loads of other resources on the web, such as these: The Bread Oven: Symbol of Colonial Liberty/A Large Clay Oven, Building and Using a Medieval-Style Hemispherical Bake Oven and The clay oven – how to build a clay oven in eight steps. The page even includes pizza recipes!