Lay an avocado on a cutting board and slice it in half lengthwise while rotating it by following the curve of the pit. Remove the knife and gently twist to separate the two halves. Insert the back of the knife blade into the pit and twist to remove it. Cut slices horizontally and vertically in each half, then scoop out the cubes with a spoon. Or, alternately, slice each half horizontally to create quarters, then peel away the skin. Then dice each quarter into cubes.