Preheat oven to the warm setting (about 200°F) and line a baking sheet with foil; keep it nearby to hold cooked flautas warm.
Pour enough oil into a large saucepan or deep skillet to measure about 3/4 inch deep and heat over medium until it reaches 375°F.
In a medium mixing bowl, combine the shredded chicken, Mexican blend cheese, salsa, diced chiles, garlic salt, and pepper; mix until evenly combined.
Working with about four tortillas at a time, place a tortilla flat and add a heaping spoonful of the chicken mixture along the center, then roll tightly and secure with a toothpick; repeat with remaining tortillas.
Using tongs, hold each rolled flauta in the hot oil briefly until it firms, then release it to fry; cook several at a time until golden brown on all sides, about 2 minutes total per flauta.
Remove fried flautas to a paper towel–lined plate to drain and immediately season lightly with salt.
Transfer cooked flautas to the foil-lined baking sheet and keep warm in the oven while you finish frying the rest.
Serve the flautas warm with shredded lettuce, chopped tomatoes, green salsa, guacamole, and Cilantro Ranch dressing.