It is not super-detailed,
(although it still turned out to be pretty long)
but I hope it explains the main ideas:
https://paper.dropbox.com/doc/DefCon-CTF-2020-ooo-flag-sharing--A0I~j7vZ3aoLA6d9rZOfGi4uAQ-a69qqRwBINkdCEVfNUN1S