Cut the watermelon into 1-inch wide slices (like you would serve to guests); remove the rind and any green/white flesh.

Cut the slices down into 1-inch cubes.

Place in a dehydrator set at approximately 135 degrees for 24-36 hours (you could also try in a 200 degree oven and let me know how that goes, but there is so much water in fresh watermelon that using the oven most likely would not be worth the trouble).

Store in a container lined with paper towels, if you're trying to make them last or something.

Try sprinkled with cayenne pepper, too.