How to get Face ID on the iPhone X to try again when it misses your face

I’ve been using the iPhone X for about a week, and, like Nilay Patel said in his review: “The good news is that Face ID generally works great. The bad news is that sometimes it doesn’t.”
I’ve been trying to figure out what to do in those cases when it doesn’t. And, thanks to a complaint on Twitter (which, as I always say, is what Twitter is for), I have an answer.
But first, my overall take is that when Face ID works, it is magically better than Touch ID. Your