Preheat the oven to 325°F. Line two large, rimmed baking sheets with parchment paper.
Wash the kale and dry it thoroughly using a salad spinner, clean kitchen towels, or paper towels. Dry it REALLY well. If it's not truly dry, it won't crisp up as it bakes. Cut the stalks off and tear the kale leaves into bite-size pieces. After cleaning, you should have about 5 ounces of kale leaves.
Spread the leaves in a single layer on the prepared baking sheets. Generously spray them with olive oil and sprinkle them with salt and garlic powder.
Roast the leaves until dry and crispy, 20-30 minutes (see notes below). It takes a while for the leaves to become crispy, so please be patient. At first, they just wilt. But slowly and gradually, they crisp up.
Serve immediately.
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Notes
Some of the kale leaves will get crispy faster. So, start checking on them after 20 minutes, and remove the ones that are done to a plate. The very stubborn ones might take as long as 30 minutes to dry out and become crispy.
Be generous with the olive oil. It adds flavor and helps the kale become crispy.
Like many homemade snacks that lack preservatives, the crispness of these chips is relatively short-lived. So, I recommend you only make as many as you will eat that same day. If you must store these chips, once they are completely cooled, place them in an airtight container or in a tightly sealed resealable bag and keep them on the counter for 1-2 days. I don't recommend freezing these chips.