Preheat oven to 250 degrees. Rinse kale and remove leaves from thick spine. Discard spines. Dry kale leaves with a paper towel and tear kale into large pieces. Toss in a large bowl with olive oil, salt and pepper. Arrange kale leaves in single layers on 2 baking sheets. Bake in oven until moisture is evaporated from the kale and it is crispy like a potato chip, about 30-40 minutes.