These are even better the second day!
Combine the cumin, oregano, black pepper, and salt. Rub all over the pork roast.
Place the pork in slow cooker (fat side up); spread onion, jalapeno pepper, garlic and cilantro all around it.
Combine orange juice concentrate and lime juice and pour around the roast. Cook on low heat for 8-10 hours or on high for 6 hours. The meat should be very tender and falling apart. Remove from the crock pot and let cool. Shred the pork using an electric mixer.
Place meat back into juices and refrigerate until the next day (for best results).
Reheat the following day in the juices and use as desired.