Rinse the pork shoulder under running water and pat dry with a paper towel. Mix salt, pepper, cumin, chile powder and oregano, then pat spices onto all sides of pork shoulder.
Add onion, garlic and chicken broth to bottom of a slow cooker, then add pork shoulder on top with fat side up. Squeeze orange and lime into slow cooker, then cook on low for 5-6 hours or until the meat has reached at least 145 degrees and can easily be removed from the bone and shredded.
Pre-heat oven to a broil and line baking sheet with aluminum foil.
Arrange halved tomatillos on baking sheet, cut side down. Add poblano peppers/Anaheim chile peppers cut side down on the same pan. Spray lightly with olive oil. Broil for 8-10 minutes until skin begins to blister.
Remove skin from peppers and pulse in a food processor with roasted tomatillos until mostly smooth.
Shred the pork and discard the bone and any connective tissue or fat that remains. Return shredded pork to slow cooker. Add chicken stock, tomatillo mixture and hominy and turn heat on slow cooker to high for 30 minutes.
Serve with desired toppings (definitely don't skip the limes and cilantro!).