Begin by preparing the filling at room temperature. In a large bowl, combine ground chicken (giniling na manok) or pork, finely chopped green onions (sibuyas dahon), drained and chopped water chestnuts (kastanyas), shredded carrots, minced garlic (bawang), soy sauce (toyo), salt (asin), and ground black pepper (paminta). Mix thoroughly but gently. Test the seasoning by frying a small portion and adjust if needed.
For assembly, carefully separate your spring roll wrappers (balat ng lumpia), keeping them covered with a damp cloth to prevent drying. Place one wrapper like a diamond on your work surface. Put about 1 tablespoon of filling near the bottom edge. Roll tightly, folding in the sides, and seal the edges with water. Cut into 3-inch pieces. Continue until all filling is used.
Heat oil in a deep pot to 350°F (175°C). Fry the lumpia in batches, being careful not to overcrowd the pan, for 3-4 minutes or until golden brown. Remove with tongs and drain on a wire rack, not paper towels, to maintain crispiness.
Serve hot with sweet chili sauce (suka at sili), banana ketchup, or traditional vinegar-garlic dip (suka at bawang). Uncooked rolls can be frozen for up to 3 months - do not thaw before frying, just add 1-2 minutes to cooking time.