Spiced Beef Lettuce Cups

Name: Spiced Beef Lettuce Cups
Ingredients: 1 1/2 teaspoons cumin seeds; 1 teaspoon red pepper flakes, plus more for topping; 1 pound lean ground beef; 2 tablespoons plus 2 teaspoons soy sauce; 1 tablespoon plus 1 teaspoon cornstarch; 3 teaspoons oyster sauce; 1/2 teaspoon baking soda; 1/2 red onion, cut into 1-inch pieces; 2 cups snow peas (about 6 ounces), halved on the bias; 2 tablespoons vegetable oil; 2 stalks celery, thinly sliced on the bias, plus 1/4 cup leaves; 1 head Bibb lettuce, leaves separated