A brick arch in front of the doorway will help protect your oven from knocks.Once the first layer is dry you can set about building it. Grab ten bricks and half a bucket of sand-clay mix. You’ll also need about a bag of sand for a former.
Build the former in the front of the cut door, extending to the edge of the base and then build the arch , alternating sides with plenty of adobe mix to stick them together. Ending with the key brick at the top – don’t worry if it takes a couple of goes to get it looking balanced. We put some bricks in front to help hold the sand form.
After a couple of hours, cut a round hole for the chimney about 5″ diameter. A few days later remove the sand former and do another firing to dry it and also check the chimney hole is right! You can then build the chimney up a little with some clay-sand mix. We used an old length of boiler flue (4″ dia) during the last stage to increase the draw and get the smoke out of my eyes!