Lately I've been thinking of recording myself writing my blog posts either as a screen recording or manually on a typewriter (latest hobby).
Hopefully others are thinking about this too although I don't know if there is a solution that isn't going to involve a fair bit of extra work.
Edit: another approach I take is I just write and don't revise much anymore. Feels like the more polished something is the more people suspect it. Although I guess you could just prompt that in too.
Other than that: 1) I typo a lot 2) I think I have my own voice in writing, which is recognisable 3) Likewise in art or music, even perhaps code
If your genuine human-made writing uses tyle guides that sprinkle em-dashes unnecessarily and uses forms such as ”Honestly? Blah bla blah.” the problem is not AI. Read Hemingway or Wilde or anything please.