You might be interested in Michael Tommassello's "The Evolution of Agency." See my response to David Green above.
It is trivial to describe how both consciousness and free will have survival value, so I won't get into that. Natural selection can and will give rise to anything that has survival value. That materialists (nor anyone else) can't describe or even imagine how neurobiology gives rise to free will is irrelevant. Nature does not care if we understand how it works.