Preheat oven to 350°F.
Heat oil in a large skillet over medium heat.
Add flour and whisk together with the oil to combine into a roux.
Cook and stir roux for about 1 minute to cook off raw flour taste.
Add the chili powders, cayenne pepper, garlic powder, oregano, cumin and salt to the pan.
Whisk everything together until the mixture resembles clumpy red sand.
Pour in chicken broth and whisk until smooth.
Whisk in water and bring the mixture to a low simmer. Simmer until sauce thickens. Whisk in more water if sauce gets too thick.
Remove from heat and allow sauce to cool slightly.
Dip each corn tortilla in the sauce to coat. Lay the tortilla in an oven safe casserole dish and place about a ¼ cup of shredded cheese in the center of each tortilla. Roll up the tortilla around the cheese.
Continue until the pan is filled with cheese filled tortillas.
Pour any remaining sauce over the tortillas in the pan.
Top with remaining cheddar cheese and sliced olives.
Bake for 30-40 minutes until heated through and cheese is melted and bubbly.
To serve, top enchiladas with sour cream if desired.