In a large pot, warm the oil over medium-heat until warm, whisk in the flour, then add in the minced garlic cloves. Mix in the diced tomatoes, dried oregano, chili powder, cumin, cayenne pepper, salt, and water.
Allow the sauce to simmer on low-heat covered for up to 2 hours. If you do not have 2 hours, allow it to simmer on medium-heat for 20 minutes.
Serve with your favorite enchiladas, or store in the refrigerator for up to 2 weeks