I can recommend starting a blog. The big thing, at least for me, is it that incentivises you to finish side-projects and complete thought pieces (at least finish/complete them enough to be able to write about them). Prior to starting my blog I'd years and years of unfinished and undocumented, but potentially quite interesting and/or innovative, side-projects.

Just to add - for technical folks a blog can be free and relatively easy to setup and self host with something like Hugo or Jekyll on GitLab or GitHub pages.