how do you find those companies?
and of course, word-of-mouth / loose social connections.
Linked-in recruiters. Say what you will about the constant cold emailing, if you set sane guidelines for them (only interested in 99-100% remote positions with comp above $x, using y or z technologies) there is an entire industry of people who will go and do a lot of the work for you. Just make a copy/pasta of your desires and reply to their copy/pasta with it; ask for job descriptions up front along with comp ranges, once they show something you like you can move forward with actually getting on the phone with them.
This shouldn't be your only lead generation tool during a job search, but it is a ruthlessly effective force multiplier.
AngelList has the largest amount of remote jobs right now out there
(Disclaimer: work at AngelList)
I found a less serious crowd compared to indeed or linked-in about hiring now. Previously when working full time I connected with a founder over a two year period and ended up working on a year long project.
What's the best way of connecting through AngelList? Are most people connecting over a period of time or do you find most are using it like a job board where they try to fill a position asap?
Also having a good reputations with other engineers who also work remotely, they'll get you in places you wouldn't have heard of otherwise.