Roast the chiles in a dry cast-iron skillet over medium heat, in batches, until they soften and turn aromatic. Cool, then remove stems and seeds.
Transfer chiles to a deep saucepan, pour the stock or water over them, bring to a boil, then reduce and simmer for about 10 minutes.
Remove the pan from the heat and let the chiles rest, about 15 minutes, so the skins loosen.
Puree the chiles with their liquid, working in batches.
In the skillet, melt the fat over medium heat, add garlic and flour, and cook stirring until golden.
Add the pureed chiles, stir quickly as the sauce spatters, reduce heat, add oregano, and simmer for 5 minutes. Salt to taste; add a teaspoon of honey if bitter.