In a shallow bowl, stir together flour, 1/2 teaspoon salt, and 1/4 teaspoon black pepper; set aside. Place a chicken breast half between 2 pieces of plastic wrap. Using the flat side of a meat mallet, lightly pound chicken to about 1/4 inch thick. Remove plastic wrap. Repeat with remaining chicken breast halves. Lightly coat chicken pieces on both sides with flour mixture; shake off excess.