Place the rice water and salt into a medium saucepan. Bring to a boil, cover, and reduce to a simmer. Cook for 40 minutes. Remove from the heat and let it sit, covered, for another 10 minutes.
Pre-heat the oven to 250ยบ.
Spread the rice out onto a small baking sheet. Bake (dehydrate) in the oven for 2 hours. The rice should be dry and hard when it's done. Place the rice into the fridge to cool off for at least an hour.
The last step is the most important, to puff the rice. In a medium saucepan, add enough oil so that it comes up to about 1/2" on the side, and heat the oil over medium heat until it's shimmering. Test to make sure it's ready by adding a single piece of rice to the oil. If it sizzles all around the rice kernel, then it's ready. Add about half of the rice to the pot and cook for about 30 seconds, just until the rice puffs up. This happens very quickly, and you do not want to overcook it, otherwise the rice will be too crunchy. Use a slotted spoon to remove the rice and place it onto a paper-towel lined plate. Do this until all of the rice is puffed.