My favourite implementation of a fingerprint sensor I've seen is to have the lock button on the side be a fingerprint sensor, as done in the Samsung M51. You are going to put your finger in it to turn on the screen anyway, and it is in an easily reachable place, without being accidentally triggered. It can also be used as a swipe input, like a back sensor. I do miss the status LED on my old Samsung S7 though. Its too easy to miss when a message comes without it.