How do I ask out a guy while he’s at work?

I’m interested in this guy that works at Whole Foods, and I want to ask him out on a date. We are not coworkers, and I only see him while he’s at work.

How do I approach him? Should I just go up to him when he’s not too busy and ask him out, or should I give him a note with my number so that I’m not putting him on the spot?