I'm 100% remote since 5 years now. I rolled into it by relocating and having my biggest client OK'ing me working from abroad. This still seems to be the easiest way to convert to being a remote employee to me, build trust with a company IRL and ask to relocate.

After that contract stopped I applied to about 20 jobs from job boards such as Weworkremotely and Remoteok with the proposition that I could work with them on a freelance base. I got only one callback out of those, did a technical interview and started working with them.

Since then I've switched several times, it gets easier as you build a network of people working remotely that can give you a tip once a position opens up and that will vouch for you.