Combine the gallon of water and kosher salt in a 8-quart pot and place over high heat. Just before the water boils, combine the remaining 2 quarts of water and the ice in a separate container. Set aside.
Once the water boils, add the peas and cook for 1 minute. Immediately drain the peas in a colander and then transfer to the ice water. Shock for one minute. Pour the peas back through the colander and transfer to a half-sheet pan lined with three 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 2 hours. Once frozen, transfer them to 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 for up to 3 months.