Create your own community where you are the only one able to post. That's it.

You can't on Lemmy, but can on mbin. I saw someone else mention just post, which will work for it, but I also just have a second account on a microblogging fedi platform for that, and that's what I'd actually recommend for it. "You don't need multiple accounts on the fediverse" yada yards, but there are certain instances where it's helpful to have multiple, like this one xD

Mbin let's you do that. Well, it lets you create microblog posts which aren't scoped to a specific community. Not ones only visible on your profile.

The big issue there is that at that point, whether it's a Piefed/Lemmy implementation or Mbin's, you're having to deal with Mastodon's main federation problem. Which is that your post only goes out to your personal followers, otherwise it stays on your local instance. Which means you need an existing personal following if you want it to federate anywhere. The threadiverse usually has the luxury of having relays in the form of communities, but with self posts, you don't have access to that luxury.

I think making a personal community, throwing it at lemmy-federate, and then posting it there really works best in this case. Lemmy-federate uses actors on various instances to subscribe to your community to ensure the posts get federated there.

If that's something you're going to be doing a lot, maybe look into starting a Mastodon account or some other service more specifically tailored to blogging?