In a large, heavy-bottomed pot heat the olive oil over medium heat. Once shimmering, add the onions, carrots, and celery and cook, stirring often, until the onions are translucent and the edges begin to brown, about 7-8 minutes. Add the garlic and cook until fragrant, about 30-60 seconds.
Stir in the chicken stock, tomatoes, jalapeños, ground cumin, ground coriander, salt, pepper, and chopped cilantro.
Cut 6 corn tortillas in half, and then cut the tortillas crosswise into 1/2-inch strips. Stir them into the soup along with the rotisserie chicken. Increase the heat to medium-high and bring the soup to a boil. Once boiling, reduce the temperature to low and simmer for 25 minutes. This will give the soup time to thicken a bit. While the soup simmers, make the tortilla strips.
MAKE THE TORTILLA STRIPS:
Pour the canola oil into a 10-inch skillet and heat over medium heat. Test to see if the oil is ready by flicking a couple of drops of water into the oil. If it sizzles, then the oil is ready. Add half of the tortillas to the hot oil and cook until golden brown, about 1-2 minutes. Use a slotted spoon to remove the tortilla strips to a paper towel-lined plate and sprinkle the strips with salt. Repeat with the remaining tortilla strips.
Ladle to soup into bowls and serve with the tortilla strips, cheese, sour cream, cilantro, and avocado.