Could 'free will' be random thoughts filtered by design selection?

I know the above suggestion has evolutionary connotations, but I'm trying to make sense of Sam Harris' neuroscience discovery 'that we are not the authors of our own thoughts' and its implication, that 'free will is illusionary'. Could it be that although thoughts do randomly pop into our minds, we somehow consciously stream them in a certain direction and select those that appeal to our reason, from which we formulate a conscious idea or decision. It seems to me that reducing our thought processes to simple manageable bits of information for experimental purposes does not prove much about something as complex as the human mind. After all, from the perspective of our mind, we believe we possess free will, and our belief in the results of experiment must also satisfy that same mind. Is a belief from outside the mind and about the mind, going to supplant a deeply held belief within?