Mine is thumb knuckle under my ear in the groove of my jaw. This is where I needed to be to get good alingment, once I got aligned, magic began to happen, bow arm was solid, and I had a better release.
Just my opinion but I think that when you develop your anchor you should first get alinged properly, THEN find a repeatable anchor in that position. I started with index finger in corner of the mouth just because that is what people told me to do, if I would have begun from good alingment, it would have saved me years of mediocre shooting.