Wash the rice in a large bowl with warm water until the water runs clear. This can take up to 15-20 minutes of washing.
Cook the rice according to the instructions on the packaging.
Preheat the oven to 145°F. Spread the cooked rice in as even a layer as you can on a nonstick baking sheet - it's okay if the rice is lumpy.
Bake the rice until completely dehydrated, about 8-10 hours. The rice should be hard and crispy.
Use the back of a wooden spoon to crush the rice into individual grains as best you can - it's okay if there are some small clumps, but the chunks should be smaller than a watermelon seed to cook properly.
Once the rice is completely dehydrated, heat the oil in a wok to 425°F - 450°F. Prepare a large baking sheet with paper towels. Have a sieve handy.
Working in small batches no bigger than the head of the sieve, fry the rice about 1/4 cup at a time for 3-6 seconds. Quickly remove the rice from the hot oil to prevent it from overcooking. Overcooking the rice will cause it to return to a hard state - it should be light and crispy.
Transfer the cooked rice to the baking sheet lined with paper towels to absorb excess oil.
Place the puffed rice into a large bowl and season generously with salt, Korean chili flakes, chili flakes or Tajin, and black sesame seeds. Toss gently to combine. Serve while still warm. Enjoy!