You need 4 other players to sign it yeah. Random people or friends, either works. Basically you target someone, then right-click the charter and request signature.
Just get 4 other non-Guilded people to sign it. No shortage of that…
Just make sure you KICK those people out of the guild once made.
I had my own Bank guild, didn’t kick those people that signed the charter… took a long break to come back finding my bank character was no longer the GM having it automatically pass onto someone else who kicked me out of the guild. They effectively stole 20m worth of TCG stuff and other things from the guild bank.
They would need not to be in a guild and to be your realm or Saurfang or Terokkar (the 3 realms are connected.) I would ask them first, don’t just present them with it.
You can either just ask randoms but many expect gold in return or just get four friends to make characters on your realm, sigh the charter and you’re done.
This rather archaic system is a little anachronistic these days. It’s about time it was drastrically changed (even if they dropped the signatures needed from 10 years ago). If they wished to keep this as a system than 1 signature ought to be enough these days. Most players could get 1 signature fairly easily. Personally I’d remove the need for signatures altogether.