Scoop the powdered ancho chile into a blender or small food processor. Bring 1 ¼ cups water to a boil, pour over the chile, loosely cover the blender or secure the top of the processor and pulse to blend thoroughly. In a small microwave-safe bowl, collect the garlic, cover with water and microwave at 100% for 1 minute. Drain and add to the blender or processor, along with the spices, oregano, vinegar and 1 ½ teaspoons salt. Process until smooth.
Place the ribs in a single layer in the slow cooker and spoon in about half of the adobo. Set the slow cooker to high, cover and cook for four hours. In a medium-size bowl, add the sliced fennel, diced apples and lime juice. Season with salt, usually about 1/2 teaspoon.
After four hours, remove ribs from slow cooker and pull the meat from the bone. Set a large (10-inch) skillet over medium heat and add the oil. Add the rib pieces and spoon in some of the leftover juices from the slow cooker, cooking until the pork sears, about 2-3 minutes.
Scoop the rib pieces into a warm corn tortilla and garnish with the slaw.