Place it at the cut where a page changes, before a bell ding marks the new section, and follow a camera shutter when a photographed page appears. That order keeps the transition clear: the turn first, the marker second, and the photo sound only when an image is actually shown.
About this sound
This is a short, just-over-a-second recording of a single sheet of paper being flipped over, with a light, dry rustle and a soft snap as the page settles. It feels calm and focused, like turning to the next chapter, and it works as a small, tidy punctuation mark rather than a loud effect.