The correct method is to dehydrate pitted black olives in a dehydrator at 65 degrees Celsius for 24 hours or until crunchy.
I used a "short cut" method of utilising semi-dried black olives and a mini toaster oven. The result is crunchy but with a slight earthy-burnt taste due to the high heat. The choice is really up to you but I prefer using this method when I'm in a rush or plating an impromptu dish.
Half the semi dried olives and remove the seeds. Place in a mini toaster oven and toast for 5 minutes or until they feel hard or crunchy to touch. Results may vary with different toasters but your aim is always the same so keep checking. Careful not to "over-toast" them or else they'll be too burnt to serve.
Use a mortar and pestle to roughly grind the olives into a soil-like texture. It doesn't need to be too fine like powder.