Step 1 Wash the chile pods, removing stems and seeds. Place the chile pods in a saucepan with the water and bring to a boil, then reduce the heat and simmer, uncovered, until the chile pods are very tender, at least 10 minutes. Remove from heat, and pour the chiles and water into a blender along with the garlic. Purée the mixture well, then strain into a bowl. Set aside.
Step 2 In a frying pan heated over medium-high heat until hot, add the lard, then whisk in the flour and cook until the flour is a light brown. Stir in the puréed chiles and stir until thickened. Season with salt and bring the mixture to a boil, stirring constantly. Reduce the heat to a simmer and cook for 5 minutes to marry the flavors, adding additional water, if needed, to thin the sauce. Taste and adjust the seasoning if desired, then remove from heat and set aside until needed. The sauce will keep, covered and refrigerated, up to 1 week.