Wash the pork with the juice of the lime or lemon and cool water, then pat it dry. This is something I grew up doing and it helps freshen the meat before seasoning.
Season the pork with the jerk marinade. I use my hands to really rub it into the meat, especially into the crevices. Be mindful that the marinade can irritate your skin, so wearing gloves is a good idea if you are sensitive. You can allow it to marinate for a few hours or overnight, but since we are slow cooking this, I went ahead immediately. Heat the vegetable oil in a wide pan over medium heat and add the seasoned pork. After about four minutes, flip it and continue until all sides are nicely browned. This step gives the pork color and helps seal in the juices, but more importantly it blooms the spices in the jerk marinade. Almost immediately you will get that warm scent of cinnamon, nutmeg, and allspice throughout your kitchen. Such a comforting aroma.
Remove the pork and place it in the slow cooker.
Discard most of the oil from the pan and turn the heat down to low. Deglaze the pan with the apple juice, scraping up all the flavorful bits as it comes to a boil. As soon as it reaches a boil, turn off the stove and pour this liquid into the slow cooker.
Add the salt, orange wedges, onion, bay leaves, brown sugar, pimento berries, thyme, celery, and any optional ingredients to the slow cooker.
Close the lid and cook for 4 1/2 hours on high or 7 to 8 hours on low.
After about three hours, flip the pork in the slow cooker and continue cooking.
At the four hour mark, test the pork for tenderness. At this stage it will be perfect for slicing. If you continue to about four and a half hours on high, it will begin falling apart and take on the texture of pulled pork.
Remove the jerk pork from the slow cooker and allow it to rest for about 15 minutes before slicing or shredding.
Strain the liquid, discard the solids, and skim off the fat. You can use it as is or reduce it further to create a rich sauce or gravy to serve with the pork.
Serve on sandwiches, with rice and peas, or alongside your favorite side dishes.