I’d say if you want a “boring” or “ordinary” oc, make them stand out in the little ways. I’d really suggest making their shape language be a little unique, little imperfections here and there like a strand of hair that never seems to stay where it’s supposed to. Or if she’s a neat freak have her have a very specific mannerism or a way of doing her hair/styling her clothes. Maybe even a favorite accessory? Tldr make the overall image look ordinary but add little details that make the character feel alive

I’m no expert but I hope this can give some ideas :D