99.9 percent of the time, it is the only way. However, I do sometimes headhunt writers on Medium to add them to Fanfare if I think their work is particularly brilliant. This tends to be the exception though, as generally I don't have time to look for writers.

I can occasionally be swayed by alternative pitches in the comments, if they are good, but on the whole I prefer new writers apply via the prompts for lots of reasons I won't bore you with here. :)