It might help if you visualize your disc as an airplane. Application of force and torque will cause a reaction of the airplane in the terms of acceleration (linear or angular). If you want to roll one direction you move the control stick left or right causing one aileron to go up and one to go down - this generates an aerodynamic torque that imparts an angular acceleration to the aircraft. To stop the roll the the pilot moves the control stick in the other direction.
OAT in discs is similar. Your hand can apply force and torques in all three axes. A typical throw wants only a torque applied in the spin axis of the disc and a force in the same direction of the initial trajectory. Up/down or left/right forces simply alter trajectory of the disc. OAT refer to the torque applied in either non-spin axis during the throw. Torque can only be applied when the disc is in contact with your hand, once the disc leaves your hand only the disc rotational velocity remains. Aerodynamics of the disc will then determine what happens to the trajectory. Discs that are "stable" in the OAT axis will fight to correct the angular acceleration imparted by OAT and correct back to intended trajectory. Often times the motion imparted has a nutational or precessional nature (flutter). If the disc is "neutral" or "understable" it will not be able to stop the angular rate and will turn in the direction of the OAT and alter trajectory completely.
You can produce the same anhyzer angle with OAT on a flat throw as you can with an anhyzer release. Take a neutral midrange and try to throw straight, but on your follow throw don't keep your arm in the plane of the disc, follow through on a downward angle (might take some practice). The disc will come out of your hand with an angular rate that neutral midrange can't stop. Eventually the disc will reach an anhyzer angle, stabilize and fly off on the same trajectory as if you had thrown it on that anhyzer angle.