Combine ground pork, garlic, onion, carrots, scallions, salt, pepper, soy sauce, and oyster sauce in a bowl. Mix until thoroughly combined.
Set a wrapper in a diamond shape and spoon a little over 1 tablespoon of the mixture across the lower half, forming a 3-inch log.
Fold the bottom of the wrapper over the filling and fold the sides inward.
Roll it tightly from the bottom to the top, forming a neat spring roll.
Seal the end of the wrapper with water to secure the roll. You can also use water with cornstarch or egg wash, depending on the type of wrappers you are using.
Repeat the process with the remaining filling and wrappers. If making ahead, you can freeze them to fry later.
Set a saucepan or a wok over medium-high heat (350-375° F). Add enough oil to submerge the spring rolls.
To check the oil temperature without a thermometer, dip a wooden chopstick into the oil. If small bubbles form around it, the oil is hot enough for frying.
Deep-fry them in batches until golden brown, turning as needed, for about 5 minutes.PRO TIP: For lumpia that stays crispy long after frying, start by frying them in hot oil at a high temperature, then lower the heat slightly to allow the lumpia to become thoroughly crispy without browning too fast. Drain them on a paper towel-lined plate or a wire rack. Serve them hot with your favorite dipping sauce.