Prepare a 9x13 inch pan with nonstick spray, or line with parchment paper. I prefer to use parchment paper so that I can lift the bars out when they are done, for easy slicing. In a large pot, melt 1/2 cup (1 stick) salted butter over medium heat until melted. Use a spatula to spread the butter up the sides of the pot a little bit. Add 16 ounces of fresh marshmallows. (Fresh meaning not a bag from the back of your pantry that you bought last year. Fresh marshmallows make for the softest rice krispies!) You can use large or mini marshmallows, they are the same. You will need 8 cups of mini marshmallows. Stir the marshmallows over medium heat. I like to use a rubber spatula that I've sprayed with nonstick spray, because things are about to get real sticky. When the marshmallows are completely melted and there are no lumps, remove from heat. Add 1/4 teaspoon kosher salt, 1 teaspoon vanilla, 1/4 teaspoon almond extract, and 1/4 teaspoon coconut extract. Stir it all together. Add 7 cups of crispy rice cereal. 1 cup of crispy rice is exactly 1 ounce, so you need 7 ounces total. Use the rubber spatula to stir it all together. Spray a new rubber spatula with nonstick spray if the other one gets too coated. Work quickly: as the marshmallow cools down, it makes it harder to stir. Pour the rice krispies into the prepared 9x13 inch pan. Get your hands wet, shake them off (you can also spray your hands with nonstick spray), and use your hands to GENTLY press the rice krispies into the pan. DO NOT press them down really hard. This makes your Rice Krispies hard to bite into! You just want to press them down into the shape of the pan. Be gentle! Let the rice krispies cool at room temperature for about an hour, or even less time if you don't mind ultra-gooey bars. Lift the parchment paper from the pan. Use a knife to cut the rice krispies into squares. Store any leftovers tightly sealed on the counter. They do not need to be refrigerated. They will last on the counter between 3-5 days before getting dried out. I do not recommend freezing rice crispies; the cereal gets wet and soggy from the moisture as it thaws.