Place the gallon of water and kosher salt into an 8-quart pot and place over high heat. Bring to a boil. Once boiling, add the peas and cook for 1 minute. Immediately drain in a colander and then transfer to a container with the 2 quarts of water and the ice. Shock for 1 minute. Pour the peas back through the colander and transfer to a half sheet pan lined with 3 layers of paper towels. Pat dry with additional paper towels. Place the tray in the refrigerator for 1 hour. After 1 hour, remove the paper towels and place the sheet pan on the bottom of the freezer. Leave the peas on the sheet pan for 1 hour. Once frozen, transfer them into a 1 gallon zip-top bag. Lay the bag flat on a counter and using a straw, suck out any remaining air in the bag. Label and return to the freezer.