I think the simplest fair isle thing I have seen is the headband I did:
Not exciting at all, but easy. The instructions are here:
Though the hat with Noro is called fake-isle, it is indeed real fair isle. I think the fake part refers to the fact that it looks like you did more complicated fair isle work because of the Noro color changes. It has long floats, (spaces where you work only one color for a long time), though, and it’s best if you weave in the ends with such long floats, so that adds one extra step of complexity.