The term "flake" can have several different meanings depending on its context.
1) In a general sense, it could refer to something that is not stable or reliable - for example, someone might say "he's such a flake" if they think the person is unpredictable or inconsistent in their behavior.
2) It can also mean a small piece of something broken off from a larger whole - for instance, one might speak of "flakes of snow" or "a flake of salt".
3) In some regions, particularly in North America, the term is used as slang to refer to a $100 bill (which has an image of Benjamin Franklin on it), so someone could say they got "paid with a couple of flakes."