connection from burner to outlet unclear

We build a Rocket Mass Burner 2 years ago and it really works well. Being totally raving about it and so we want to build another one. But, and this is were the question is about, with our first one we really struggled with the point where the outlet leaves the burner. I added a couple of photos. One in which one can see a little bit how we created the outlet which is a pipe that we flattened a bit because for the pipes original shape there was no space.. And an image of the video of Ernie & Erica Wisner  where I added 3 question on to.
(And the finished beauty)
If someone knows a picture or a sequence of pictures or video that shows how this outlet is done, I would be very happy with that. Thanks in advance.
Keep on burning!

Petra, yes the barrel rests often higher.


You can make all sorts of "flue transition"

https://permies.com/t/39117/rocket-mass-heaters/Transition-Area-Rebuild-Questions