Here's a recipe I've used lots:

1/4 cup lard, veg. shortening or oil.
1/4 cup flour
1/2 tsp black pepper
1 tsp salt
1 1/2 tsp granulated garlic
2 tsp ground cumin
1/2 tsp dried oregano
2 tblsp chili powder
3 cups water or chicken broth

In large skillet, heat lard to medium hot. Stir in flour and continue stirring until it turns a very light brown. This will take 3-4 minutes. Add all the dry ingredients and continue to cook for 1 minute. Constantly stirring and mixing ingredients Add broth or water, mixing & stirring until sauce thickens. Turn heat to low & let simmer for 15 to 20 minutes. Add more water to adjust the thickness to your preference. Makes enough for about 8 enchiladas. Will keep a week to 10 days in the fridge & also freezes well.