Someone who is noncommittal or agrees to everything but then never shows up and therein flaky. So flaky to the point of being almost professional in the practice of it. A professional flaky person. Hence, flake-up artist.
e.g.
Ben: "Liv! We haven't met up in ages!! Fancy meeting up this weekend? I'll be in your neck of the woods any how so we should deffo meet up for a crafty drink! You down?"
Liv: OMG! Ben!!! YES. We gotta do this! Bell me when your here and I'll come down!
(24 Hours passes and Ben arrives at agreed location)
Ben: "Hey Liv, I've just arrived! Where abouts are you?
Liv: ...
Ben: "Liv? Are you en route??"
Liv: ...
Ben: Fml....
Liv you are such a flake up artist...