Take this quote in answer to a student’s question about medieval bread for a school report (Posted on Yahoo Answers):
...all bread in medieval times was a flat unlevened bread as yeast had not yet been thought of as an ingrediant to make the bread rise. it was baked in kilns fired by wood, most prominent households would have one in the house when the bread was baked the under side became a lot harder than the top part of the bread , the harder part was given to the servents and children while the upper part given to the more important members of the household, thus they became known as the upper crust still used as a name for a class system to this day you will often hear people of more importance called the upper crust...
Besides indulging in perpetuating that awful e-mail meme, “The Bad Old Days” it is neither helpful to the student nor accurate. The discovery of yeast, leavened bread and wine/ale/mead is lost in history but even the Romans recorded that the Gauls skimmed yeast off of their ale to make bread rise (Pliny, Natural History XVIII-26).
One website I found (that I now cannot, for the life of me, re-find) asserted that since the earliest medieval text to mention salt in a bread recipe dated to the 15th-Century, salt must have been unknown or unavailable to earlier bakers. This is another one of those over-simplifications that so annoys me.
Salt? Unavailable? Unknown? Salt was a prime medieval commodity, required in large quantities for the preserving of meat and fish. Extracting salt from seawater or mining it was a major industry. A little salt goes a long way in flavoring and lightening a loaf of bread.
Even good articles talk about medieval ovens in such a way as to imply that there is no other way to cook dough. To we modern Americans, it may seem like bread must be cooked in an oven, but that is simply not the case.
Every village house would have had a fire pit/area for cooking and heating. Bread, even leavened bread, can be cooked on that fire -- either fried above it or by immersing a both under the coals, dutch-oven-style. These methods make a lot of sense to me. A specialized oven seems to require a lot of wood and resources to operate. There must be another method, smaller in scope, more personal, that the oven evolved out of.