This question came up when I was trying to explain that color is subjective. My conclusion is, color is constructed by our "Imagination", the same mechanism that produces mental images.
That discussion leads me to think if consciousness could be just like color, it was produced to fill void in our mental images: "Now I have this thing called consciousness and I can FEEL how I really have free will".
What if Imagination is first order. And everything else including complex concepts such as consciousness was simply produced out of necessity.
I acknowledge this idea is on the naive side. Pointers to further readings are greatly appreciated.
As for "Imagination", the mechanism that can produce a mental image, I tend to think of it not conscious but behave based on a collection of external sensory data, knowledge gained through previous learning activities, as well as other data (including memory) .