While simple, it can honestly be kind of fun to just go in and let them know. When I was recently laid off, it went something like this.
HR: "I know this might be a shock–"
Me: "Yeah, you're letting me go, I know. Here's my work laptop and badge, I've got all my stuff in a box outside, what do I sign? Trying to catch the next train home, so I have like 20 minutes."
It totally threw off my boss and the HR lady trying to do their sombre, dignified thing, and was pretty funny to watch.