So what is the process for creating a GOI in the wiki?
Write things with a group that the Foundation is interested in. This is a GOI.
If other authors write some stuff with the same group, or even if you write a whole lot with that group, and people like it, you might be able to get a hub to stick.
If you write some documents that originate with that group and provide guidelines for others to do so, these should be tagged goi-format and will be listed on the hub for those documents.
If your group has five articles by three authors it might get added to the Groups of Interest hub. This isn't a guarantee, because there are at least two different groups that rate by the 5x3 rule but aren't listed; that hub isn't exhaustive.
at least two
That's pretty generous. The SPC, the Daevites, the IJAMEA, pattern screamers, 1000, the mainstream Wanderers Library according to certain esoteric interpretations etc. are probably popular enough to be on there, but they're all excluded because enough people contend that they shouldn't.
Though, IIRC, back when Gamers Against Weed was getting off the ground, it was revealed that the baseline had been changed to seven articles, not five, because reasons.
Write things with a group that the Foundation is interested in.
That's pretty much it. Write a bunch of articles involving the GOI that a) are good enough to get upvotes and b) are interesting enough that people want to use the GOI.
The others have covered the literal process for making a new GOI. If you want to make a GOI that will survive, you should attempt to find some kind of story or subject matter that is A) underrepresented, and B) is not already covered better by another GOI (or the Foundation itself). Then design a GOI that is suited to that material and start writing stories featuring it.
You'll need to have a keen sense of the state of the site and good writing sensibilities, so if you're not already an accomplished writer (either on the site or outside it), I recommend directing your time and energy somewhere more useful, because it won't work.
(Of note: CWW is the most recent person I know of to accomplish this.)
I share credit with kinchtheknifeblade, but yes, I am speaking from experience.