You mean completely spontaneously or with help (Moxibustion, Pulsatilla, Webster, etc.)?
My first baby flipped back and forth a lot.
I never did anything to help because I didn't hire an OB (surgeon) and so position wasn't a concern.
Most babies are vertex by delivery. Many moms have pre & early laboring contractions to get baby's head down in labor.
If you want to nudge the process you have plenty of safe options (not ECV).
My son turned at 38 weeks. I had an ultrasound and he was still breech, so we scheduled a c-section for the next morning at 9:30. At 9:25, I was all prepped for surgery and ready to go, when my doctor came in with an ultrasound machine one last time to make sure everything was still the same. He put it on my stomach and surprise! My son was head down.
My friend did. They tried an external version (her words) at 36 or 37 weeks that didn't work, so they scheduled her for a c-section at 39 weeks. The morning she went in for the c-s, they did a quick u/s and he'd turned on his own! So they let her go home and go into labor on her own, at almost 42 weeks. She was very happy.