Popping off the risers is simple to do. Usually, you can gently wiggle them out using only your hands. However, because this is a natural product and humidity does sometimes swell wood, you may need to use a bit more force.
Flip the board over and push on the riser pegs. This should do the trick.
If they are really stuck use a golf tee or the like and, with a hammer, gently tap the riser pegs until they become loose. You can then pull them off with your hand.