You feel stupid? Welcome to the club
Everyone starts off with loads more enthusiasm than knowledge, then this transforms into hard work and dogged determination (with any luck). The idea of building a stove outside is to learn by playing with one in a safe place.Trying your first one indoors could be a short term venture if things go badly. The RMH is relatively quick to build and modify, and a good example is
https://permies.com/t/14115/stoves/Multifunction-outdoor-rocket-system
Read through lots of posts on this forum, particularly noting those by Erica and Ernie Wisner. They have done lots..
The reason approval is needed is because it is a notifiable service, and particularly it is solid fuel, and they kill more people than gas through
carbon monoxide poisoning. In the UK the flue has to exit above the roof, and for normal appliances ideally above the ridge.
I don't like all the bureaucracy any more than anyone else, but when the system collapses and people are freezing with not
enough fuel, with the knowledge and materials I will have accumulated, I can build a heater, and in those circumstances no one will care. However, I still don't want it to kill me.