The most comprehensive explanation of the "Flat Earth" theory I have seen so far is by "Vibes of Cosmos." They have made detailed maps of the "whole Earth" not just the part we live in at the moment. They claim the Moon is plasma, not rock, and acts like a mirror showing us the full map of the Earth!! May be a load of crap but definitely worth checking out
https://www.youtube.com/@VIBESOFCOSMOS