[Erik Cervin-edin]

This video, despite its creepy religious overtone, is a pretty good tutorial on how to make a magazine flip:
https://churchmediadesign.tv/after-effects-magazine-page-flip/
However I set it up by putting two pages, front/back at the same position (with a 0.1 difference in the Z axis) and same anchor point. Then I parent the front. Turn it 180 in X.

To fix the mirrored backpage I set the front end page’s orientation to
0.180.0
and the back 180.0.180

works like a charm