Slice the meat into 1/4-inch-thick-strips. The shape of the pieces doesn't matter but larger ones will be easier to grill.
Remove seeds from chilies and toast the seeds in a dry skillet until lightly colored. Put the seeds onto a plate and cool them completely. In a spice grinder or coffee mill, grind the seeds to a fine consistency. Place meat in a large bowl and add ground chili seeds, garlic, crumbled bay leaf, and enough olive oil to coat the meat. Let rest at cool room temperature for 3 to 4 hours.
Prepare a hot charcoal fire. Season the meat with salt. Grill on both sides until done to your taste. Set the meat aside while you grill the tortillas quickly on both sides to warm them. Tuck slices of meat into each tortilla and garnish with lettuce, onion and salsa.
In a large skillet lined with aluminum foil, toast the chiles over moderate heat for about 5 minutes, until they almost smoke, stirring often.
Bring 2 cups of salted water to a boil. Add the toasted chiles, garlic, and oregano. Simmer about 10 minutes, or until the chiles are soft.
Pour into a blender. Blend on low speed for several seconds, then increase to high speed for about 1 minute or until smooth. Add water to thin out sauce if you prefer.