Ooh that’s a tricky one. There’s a lot of different ways to flirt, it all depends on a few things. I’ve also never had to write this down so I’m working backwards from my own learned experience here.

Flirting is pretty close to just acting regular around someone, at least in the context you’re talking about. You need to work with implied intent, like she is with going out of her way to be around you, if it is something she’s doing on purpose a few times. You’ll have to be careful if you’re in a workplace like it sounds, don’t take it too fast, and always leave room for her to gracefully disengage. I’ve never been brave enough to risk my work for a potential connection, but that part is up to you.

First, be yourself. I know that one gets thrown around, but it’s incredibly important that you don’t suddenly start acting like someone you’re not, or do stuff you otherwise wouldn’t. If they’re flirting with you, they must like you being yourself already, and if they don’t like you being yourself, it wasn’t worth pursuing anyway.

Obviously, as you don’t know if they’re into you, you don’t want to come on too strong. In general being playful is the key, slowly becoming more comfortable with them as time goes on. Keep it fun, easy, at least initially. Light teasing, jokes, a bit of eye contact. Whatever is most comfortable for you.

In general, I would make sure they know you appreciate that they’re around, especially if they’re putting themself out there to you like you suspect. Smile at them when they turn up. Go out of your way to initiate conversation and hang out with them in turn. Comments/compliments on they way they go out of their way to spend time with you, stuff like saying it’s good to see them when they turn up. Veil it as jokes, or just be upfront with it. Be a bit warmer with how you talk to them, maybe a small gift. You want the subtext to be that you’ve noticed they put the effort in, you appreciate it, are into it, and willing to reciprocate. This is also key because this signals to them that you’ve taken their intentions as flirting, and if they weren’t going for that, they have the opportunity of de-escalating.

Keep compliments generally about stuff they have control over, stuff they’ve obviously put effort into. Jewellery, hair, clothes, how they act, their competencies. Don’t go for stuff like body or attractiveness until way way later, like after a date or two, or they do it to you first.

You can also leave casual touching a bit later, generally after you’re actually on a date, things have been going well for a good while, or if they already break the touch barrier. Women get to be a little looser with that, but if you’re a dude it’s incredibly easy to come off as creepy if they’re not 100% into it. Keep in mind there’s often a power imbalance, testosterone will likely make you stronger than someone without it, so by default women need to be careful around men. It’s important she always feels comfortable around you, coming on too strong can really torpedo things. It should be fine by the sounds of things, but just to be sure you know.

If all is going well, at some point you’ll have to turn it from subtext to text. That is, you’ll actually have to say to her face that you’re enjoying this, and want to spend more time with her. Dating is a different topic, but similar rules apply. Don’t leave it too long, but it sounds like it’s already going well, so it should be fine.

Take it easy, enjoy yourself. You might mess up, consider it an education for next time. It’ll get easier as you go.