Offer your services on platforms where self-promotion is allowed. At the same time, make content, if you do something and it's good, and if someone sees you're also taking gigs then maybe they'll hire you.
I see people making threads and linkin to portfolios or sample works on Facebook, Twitter, Reddit, Discord Servers, Tumblr, writing forums, DeviantArt's Job Offers & Job Services, some other have their prices organized on Carrd or Ko-Fi.
A lot don't even care about ghostwriting services only, I've seen writers offering themselves to write fanfiction most of the time as well