In a medium saucepan heat oil, add flour, smoothing and stirring with a wooden spoon. Cook for 1 minute. Add chili powder and cook for 30 seconds. Add stock, tomato paste, oregano, and cumin. Stir to combine. Bring to a boil, reduce heat to low and cook for 15 minutes. The sauce will thicken and smooth out. Adjust the seasonings. Serve atop your favorite enchiladas.