Heat oil in a large skillet or wok over medium-high heat. Add the spring onions and garlic and sauté for about 30 seconds, until fragrant.
Add the cabbage, carrots, bell pepper, and green beans. Stir-fry over medium-high heat for 4 to 5 minutes, keeping the vegetables slightly crisp rather than completely soft.
Stir in the soy sauce, chili sauce, black pepper, and salt. Cook for another 2 to 3 minutes, allowing any excess moisture to evaporate. Transfer the filling to a plate and let it cool completely.
Mix the flour and water in a small bowl to make a smooth, thick sealing paste. Place one spring roll wrapper on a clean surface and add about 1 to 2 tablespoons of the cooled vegetable filling near one edge.
Fold the bottom and side edges over the filling, then roll the wrapper tightly into a neat cylinder. Brush the final edge with the flour paste and press gently to seal. Repeat with the remaining wrappers and filling.
Heat oil in a deep pan to about 350–375°F (175–190°C). Fry the spring rolls in small batches, turning occasionally, until crisp and evenly golden brown.
Remove the spring rolls with a slotted spoon and drain on paper towels. Serve hot with chili garlic sauce, sweet chili sauce, or tomato ketchup.