In a large ziplock bag, combine barley flakes, blueberries, nuts, sugar, cinnamon and salt; shake to mix. (You can store the sealed bag for up to a month in a cool, dry place.) To prepare a single portion, place 1/3 cup cereal mixture in a medium microwavable bowl. Add 1/2 cup water and microwave, uncovered, for 3 minutes. Let stand for 2 minutes before serving.