Preheat oven to 375° F.
Heat tortillas until warm. Warming tortillas prevents them from cracking and breaking. You can warm them one of three ways. In the oven, wrap stack of tortillas in foil; place in a 375° F oven for 10-15 minutes. On the stove, turn a gas or electric burner on high. Using tongs, slide one tortilla at a time over the burner for a few seconds, alternating sides, until it's softened and beginning to char. Cover tortillas to keep warm. In the microwave, wrap a stack of 8 tortillas in a barely damp, paper towel; microwave on High for 30-45 seconds.
Coat each side of 4 tortillas with cooking spray. Turn a 12-cup muffin tin upside down. Nestle a tortilla in the space between 4 cups to form a bowl. Repeat with 3 more tortillas, making 4 bowls total.
Bake until firm and beginning to brown, about 12-15 minutes. Transfer to a wire rack to cool. Repeat with the remaining 4 tortillas.
Meanwhile, toss chicken with garlic powder and salt in a bowl. Heat oil in a large skillet over medium-high heat. Add the chicken and cook, stirring, until it is no longer pink on the outside, about 3 minutes. Add salsa and cook, stirring, until the chicken is no longer pink in the middle, about 3 minutes more. Cover and remove from the heat.
Fill each tortilla bowl with about 1/4 cup of the chicken mixture. Top with cheese, sour cream, lettuce, tomato and olives.