Unplug the Cuisinart blender from the wall.
Twist and remove the plastic blender body from the base.
Flip the blender base upside down and remove the three screws that hold the bottom to the base. Use a Phllips screwdriver to remove the screws and then remove the base. This will expose the motor shaft, which is a rod protruding through a fan-like object.
Insert a flat-head screwdriver into the flt groove at the end of the motor shaft and hold it in place while spinning the coupling off by hand through the front of the blender.
Screw the replacement coupling back onto the motor shaft until it is tightly in place.
Place the bottom back on the base of the blender. Insert the retaining screws and tighten them.
Place the blender body back on the base, plug the blender in and test it out.