ok here's the issue, she may think in her head that the guy doing this is some dude she's either had her eye on or some guy who's recently hit on her. So she may build all this up for someone else and then be a bit disappointed when her good friend ends up being the one. I'm not saying she doesn't want a relationship, but you may cause her to start crushing hard on some other dude.
I would suggest sending her flowers at work with your name on them and ask her to think of a place she'd like to go out to eat for dinner or if she'd like you to decide. This will get her thinking, ok is this a date? And that's your opener, she has to reply because you asked her to pick a place or tell you to pick one. Talking to her the first time after breaking this news is always going to be awkward, no matter how you set it up. Unless you have her running to the end of a pier after you sailing away on a boat, it's not going to happen easily.
So then you just gotta tell her straight up when you talk to her in the follow up call. Tell her you want to ask her on a date because you think she's the best girl you know, ever known even. Be cheesy, it goes FAR.
Now, I would never go through all this for a girl, I would just flirt with her straight up and tell her I think she's the beeznees.
And if it doesn't work out, trust me, there's a zillion soul mates out there for you.