The complexity of the circumstances required to implement the freedom of an intentionally uninfluenced 50% probability occurrence, is equivalent to the flip of a coin.
The complexity of the circumstances which God would leave to freedom of occurrence in order to implement free will, would be equivalent to the complexity of our consciousness.
In order to allow freedom of occurrence or randomosity of any scenario, you simply need to allow something to occur without intentionally influencing the outcome. The degree to which you allow circumstances to occur without intentional influence, would be equal to the degree of freedom of occurrence. Scientifically, it may be possible to calculate and intentionally cause the entirety of a set of circumstances and occurrences. Hypothetically, with this capability, in order to allow freedom of occurrence, randomosity, or chance to occur, you would simply need to allow a certain set of circumstances to occur without an intentional influence or cause of outcome.
The method of development of human consciousness (and therein the complexity of circumstances required to allow free will), would be the complexity of our consciousness. The method of development involved with evolution from the initial spark of microorganisms, all the way to human consciousness,,, is pretty complex.
So from Gods perspective, in order to create free will to the complexity of human consciousness, God could allow the circumstances of evolution to occur, without his intentional influence of outcome.
If God allowed the circumstances of evolution to occur without intentional influence of outcome; how could God then alter circumstances within the happening of evolution, which seem necessary and relative to be altered, in order to intentionally cause future circumstances within the lives of humans?
For freedom of occurrence, the only lack of influence on circumstances would need to be: with intention directly relative to the outcome of that which is being left to freedom of occurrence. Alternate alteration to the same circumstances could be placated, as long as there is that lack of intention for the specific outcome of freedom of occurrence ie. intention to cause human consciousness to function by a specific method.
God likely alters circumstances throughout the modern world which have an influence on the decisions of people who are not willing for God to alter their free will. This is not a reduction of free will, since God is not altering the circumstances with the specific intention of influencing their decisions, but altering the circumstances for another intention, of a potentially unrelated occurrence.
The principle of this concept, would be: as long as the intention is not for that specific outcome, the effects of that alteration of circumstances are still left to freedom of occurrence. This concept can perhaps be relayed to the circumstances of the development of human consciousness, and therein free will. God could potentially alter circumstances which may influence occurrence relative to development of free will, but as long as the intentions are not specifically to influence the specific result of the initial human consciousness, human consciousness would still be left to freedom of occurrence. Ie. Free Will