Consider using the Enrolment on Arrival program rather than booking an interview, that’s what I did a month ago for my interview.

Mine was at SFO but they do them at LAS as well. For what it’s worth I just followed the Global Entry signs on arrival and there was an enrolment on arrival desk in the are, I was first to arrive so got seen straight away, those following had to write their names on a list attached to a clipboard and sit waiting on some provided chairs. The “interview” involved no questions whatsoever, just handed passport to officer who tapped away at his computer a bit, then handed my passport back and said you’re all set. Three minutes start to finish.

As I say that’s the SFO experience, who knows how consistent LAS may be!