If I set up my own nameserver/and or a DNS server, How would I go about making my own custom domains? Please correct me if I am wrong about needing a nameserver/and or a DNS server
You can't eliminate the registrar and domain servers entirely, as no browser could find your domain. So no, what you want isn't really possible
A domain must be registered through an ICANN accredited registrar. That's what the ".com" or such points to, then their servers say "check domain registrar for more info"
Even if you could get this up and running, you may get in trouble (unless you create your own registrar, which is expensive and not easy)
There really would be no gain doing it yourself anyway, because Cloudflare had a global CDN you don't have, and a lot more server power