Step 1: Design the actuator you have always wanted.
Step 2: Enter the specifications
You will have to manipulate the gap height parameter to find the gap height that gives the best flux density (least power) while not exceeding whatever spatial limitations you might have. As you play with this, you will not that the equations break if you choose this parameter unusually low or high.
Step 3: Machine the stator and bobbin
A couple of tips on this step. Machining a deep pocket in Iron (or soft steel) for the stator is a pain. As a alternative, you may machine a cylinder and a disc. Place the cylinder on a hot plate and the disc in ice water. After the cylinder is at 500 oF and the disc at 30 oF, slam them together using an arbor press (exciting). The bobbin should be made out of aluminum or plastic. Be careful while assembling the magnet and flux puck into the stator cup. It is recommended to machine a guide for the magnet and puck so as to avoid losing digits.