Pre-heat oven to 375 degrees. In a large bowl, toss the shredded chicken with cumin, red pepper flakes, 1/2 cup salsa verde, and 1/2 teaspoon salt.
Warm the tortillas on a griddle or skillet on both sides until softened keeping them warm in a cotton kitchen towel as you go along.
Lightly grease the bottom and sides of a 13 x 9-inch or 12 x 8-inch baking dish with olive oil.
Spread 1 cup green sauce lengthwise down the center of the baking dish.
Place about ⅓ cup of chicken mixture down the middle of a tortilla and roll tightly. Place seam-side down in the baking dish. Repeat with each tortilla. Cover the rolled tortillas with remaining sauce. Sprinkle the remaining cheese down the middle of the tortillas so the edges get brown and crunchy. Do the same with the queso fresco, if using.
Cover and bake until heated through and cheese is melted, about 20 minutes. If you want the cheese to lightly brown, put back in oven uncovered for another 5 minutes.
Serve immediately with desired toppings and sour cream on the side.