Clay Oven - Baking Buns This oven is built as an example of the type which was common to western Canada and made from local material. A framework of willow is constructed, then plastered with a mixture of clay and straw. The fire is built inside the oven and requires about one hour of preheating before cooking. The glowing coals are left inside to help maintain the heat. All types of food can be cooked in these ovens and bread can be baked, 32 loaves at a time. This oven is used to bake bread and buns.