Thats really how it goes. The power from slap shots actually comes from full upper body motion and stick flex due to your lower hand on the stick. When you do a slap shot you actually contact the ice just behind the puck and flex the stick into a bow shape with your bottom hand. The stick then "snaps" straight and that combined with the force of your upper body rotation provides the power of the slap shot. A wrist shot is not much different but you just keep the stick on the ice behind the puck. Use the flex of your stick again to generate power.
Your right hand does most of the work but your left hand is crutial in controlling the flex of the stick as well. Oh and remember when shooting, the puck will go where you point your blade so when shooting point to where you want the puck to go with the tip of the blade.
Have fun!!
Berz out.