Prepare the Vegetables: Wash and dry the cabbage, carrot, bell pepper, bean sprouts, and green onions. Shred or slice the vegetables thinly so they cook quickly and fit easily inside the wrappers.
Cook the Filling: Heat vegetable oil in a large skillet over medium heat. Add the minced garlic and grated ginger, cooking for about 30 seconds until fragrant. Add the cabbage, carrot, bell pepper, and bean sprouts. Stir-fry for 3–4 minutes until the vegetables soften slightly but still retain some crunch.
Season the Mixture: Add the green onions, soy sauce, sesame oil, black pepper, and salt. Stir well and cook for another minute. Remove the skillet from the heat and allow the filling to cool completely. Drain any excess liquid before assembling the rolls.
Make the Sealing Paste: In a small bowl, mix the flour and water until smooth. This paste will help seal the spring roll wrappers and prevent them from opening during cooking.
Fill the Wrappers: Place one spring roll wrapper on a clean surface with one corner pointing toward you. Add about 2 tablespoons of cooled filling near the bottom corner, leaving space around the edges.
Roll and Seal: Fold the bottom corner over the filling, fold in both side corners, and roll tightly toward the opposite corner. Brush the final edge with the flour paste and press gently to seal. Repeat with the remaining wrappers and filling.
Preheat and Arrange: Preheat the air fryer to 375°F for about 3 minutes, if required. Lightly spray the basket with oil. Arrange the spring rolls in a single layer, leaving space between them. Lightly spray the tops with oil.
Air Fry Until Crispy: Cook at 375°F for 10–15 minutes, turning halfway through, until the wrappers are golden brown and crisp. Work in batches if necessary. Let them cool briefly before serving.