At one point, if you’ve created your own hashtag for features, people will start submitting as you grow. The more popular you get, the more you get the work done for you by people who want you to feature their work.
I’m at that point now with just over 5k followers. I’d say it started rolling in at 3k without me needing to do anymore work beyond approving/denying and modifying captions. Some days are slow, maybe 1 submission via tags, others I’ll get someone who goes back through their entire history and tag me in every single one of them… which can be annoying when they’re all awful shots, but hey it’s free advertising too.
Sometimes they’re totally unrelated, probably people randomly using the hashtag and not tagging my account, but it’s easier to delete a post from the draft list than it is to research and contact people to feature, and then wait for approval… by just about every possible stretch of the imagination.