Free Will ironically is a fundamental doctrine of even the most authoritarian of religions. Free Will is simple to explain at any level, be it sociocultural, political, individual, internal, religious, metaphysical, scientific or cosmological..
Life is like a video game. The parameters are all pre-programed by various circumstances at any level of analysis or perspective you prefer. We are completely free to make any and every decision, but our outcomes are entirely preconceived, even if at random, by the circumstances and the parameters. Just as we are free as 4 dimensional beings to move our hands in time and space, but at the same time fundamental forces such as gravity entirely determine the parameters of every infinitely possible movement..
The Church teaches similar, but replaces gravity with God
