Bring the 6 cups of water to a boil. Remove from heat.
Add the dried chiles making sure the chiles are submerged under water, I use a small plate to weigh them down. Allow for the chiles to reconstitute which takes 30-60 minutes. You can also do this in the evening and allow for the chiles to sit over night.
Once your chiles are nice and soft (see picture above) strain the water and discard.
Place the strained chiles, onion, garlic, broth, sea salt, oregano and oil in the blender. Preferably a high power blender like a Vitamix or Blendtec.
Blend for 1 ½ minutes on high until nice and smooth.
Place in saucepan and bring to a boil. Once the sauce boils reduce to a simmer and cook for 10 minutes.
Will keep in refrigerator for 1 week or you can freeze.