Not OP, but the answer to this is almost always "network with people who will pay you to freelance." This assumes you already have the skills/knowledge worth paying a freelancer for.
Not really. Getting a traditional job is a lot easier, because there are job boards and such. However, those are notoriously horrible for freelancing.
Saying, "Just go network" glosses over a whole lot of exactly how to do that. It's like, if someone asked, "How do you make a good income investing?" and your response was just, "Pick a few good companies." That's great and all, but it completely ignores the process of actually doing that.
It really just means putting yourself in places where you're likely to find people who would hire a consultant, and then getting them to a) like you and b) believe that you're competent at whatever you're trying to bill for. It's not necessarily an overnight thing, but after doing this consistently for a little while, people will start asking if you can help with XYZ as the need arises.
If you don't know where else to start, go to a local user group, or better yet, present at one. It only takes one visit to see how low the standard is at most of these things, the organizers are usually just happy to have someone willing to present, so you don't have to worry about not having anything substantial or good to present.
I had a full-time consulting income for several years predominantly from just following ads for freelancers on Craigslist, in a relatively pedestrian market. I didn't even do the basic networking stuff that is still a very good idea. The hardest part of breaking in is having the gumption to get it kicked off.
What if I have no clear idea of how to do this, and the standard advice for that problem starts with stuff I don't know how to do (e.g. talk to people like a normal human who craves face-to-face social validation)?
Too broad of a question, in my opinion, but yes, I have successfully freelanced at various times and with various skills and knowledge used over the last 25 years. Each time it was knowing the person beforehand and being asked to perform consulting. Long ago it was through my parents' networks, and more recently through professional contacts.