Step 1 Remove the stems and seeds from the chiles and place the peppers in a glass bowl. Pour boiling water over to cover by 3 inches and let them soak until very soft, about 30 minutes.
Step 2 Drain the peppers and place them in a blender with the garlic and oregano. Strain the soaking water and add 1 1/2 cups to the blender. Puree until smooth. Strain the mixture through a sieve into a clean, shallow pie plate; season with salt and set aside.