To the insert of a slow cooker, add the chicken thighs and sliced onion. Sprinkle on the chili powder, cumin, garlic powder, onion powder, chipotle powder, Mexican oregano, and salt. Use a spatula to mix well and incorporate the spices evenly. Add the orange juice on top and stir to combine.
Cover the slow cooker with the lid and cook on high for 4 hours or low for 6 hours. After the chicken has cooked, use a wooden spoon to break up the chicken. Press the back of the spoon into the chicken and against the side of the slow cooker to break into shreds. Stir the meat to incorporate it into the juice.
