I guess I could just gradually ramp up the flirtiness/sexualness, although I'd like to hear some specific details/tips.
That's probably the best way to do it, though I think we would need more context. Is this a co-worker? A neighbor? Some platonic female friend from your leisure time?
If you're in a well established friend zone, you could ramp things up, but that's not a high probability play. If it's a mere acquaintance, the ramp up could work, but there are better uses of time.
Frame is everything. Start every relationship with a sexual frame.
I don't have female platonic friends. I don't hit on my female co-workers.
Former co-workers are a thing. You are free to ask someone out if she's leaving the company or you are leaving the company. It's ideal to do that under a resignation scenario than termination. Also, if either she or you are terminated, you might not have the luxury of having time to do that in-person, and that's if you're being terminated in-person these days. A lot of terminations now are done over video conferencing software.
Also, as a terminated guy, you have zero SMV in her eyes. Male SMV is closely tied to employment. If she was terminated, male SMV remains healthy, but there are other problems. She might not be in a frame of mind to date. If she was terminated as part of a mass layoff at work and you survived the mass layoff, you might not be in a great place either because now you're going to need to do a job search in a lot of cases.
In white collar work, most companies try to do everything they can to protect their female talent. Males are more likely to be laid off first. The least likely to be laid off are minority females, whereas the most likely to be laid off are White males. Female talent is only laid off if their performance is absolutely terrible and/or the company is in a very bad place, likely a sinking ship.