Free will is consistent with neuron function. The brain expends the lion's share of its metabolic energy, pumping and exchanging sodium and potassium ions across the neuron membrane. The end result is, these ions are separated and segregated on opposite sides of the neuron membrane.
This energy intensive segregation of ions, causes a lowering of entropy at the level of these ions. In other words, left to their own devices, these segregated ions would prefer to blend and randomize. The constant ion pumping and resistance of the membrane, provides a way to lower their entropy and thereby create a lingering entropy potential at the membrane. The second law, attempts to increase this entropy, leading to neuron firing and some randomization, that is the foundation for will. Neuron firing leads to new branches and synapses.
This is not the whole story. A key component of the brain is water. Sodium and Potassium ions impact water in different ways. Sodium ions are Kosmotropic meaning they create more order in water, than water creates for itself. Potassium ions are Chaotropic, which means these ions create more chaos or disorder in water than water creates for itself. The segregation of these two ions, not only creates ion entropy potential, but it also creates an entropy potential within the water, with water entropy highest where the potassium ions accumulate. The water, which is continuous on both sides of the membrane sees an entropy gradient.
Since all these ion dynamics occur within water, and the fastest ion within water, is the hydrogen proton of water; pH affect,, the water responses to the dual entropy potential much faster than the movement of the sodium and potassium ions. Water is already making needed changes in potential before these ions slowly move, by comparison.
This semi-independent and semi-dependent motion of water and ions adds additional randomization to the increasing entropy, especially when averaged over the various local and global water potentials, created by neuron firing sequences and neurotransmitters, dissolved in water, which tweak the water potential further.
Humans have two centers of consciousness in the brain; inner self and ego. These two centers can establish an additional gradient, in the water of the brain, from which the bulk affects called human will and choice appears.