Here is how
This looks very cool and while does not look like a "correct oven", they claim
"despite concern that it might not hold up to repeated use, the basic clay bricks and Portland cement held up perfectly. The original oven was built almost 20 years ago, and is still in service."
WOW ! This is amazing.
I never used a regular bricks for my oven internals. Even my Japanese "temporary" oven has firebricks inside.
I also always use some kind of insulation. Temporary oven has a light bricks around and they helped to keep heat inside.
My backyard oven has a TONS of insulation. First it has a Italian "fire mold" inside. There are A LOT of fiber and reflective insulation around it. Finally, it has a regular red bricks around. This mainly protect oven from elements and for decorations ( I did a sloppy job in a harry and it looks a bit rustic compare to the on on link)
But make no mistake: I put FUNCTION over look ( even so I LOVE a good look very much).
One more advice: make sure you have ENOUGH room inside your oven. You need room for wood and you need room for pizza and you need some space. While oven may look balky outside, make sure it is big inside.
My backyard oven is probably the smallest oven you should build. Smaller than that is very hard for regular use. You can find a dimensions on my blog below.