1. Start by mixing the salt, pepper, smoked paprika, and cinnamon in a small bowl to create a flavorful dry rub.

2. Generously rub the dry spice mixture all over the pork shoulder, ensuring an even coating.

3. In your slow cooker, arrange the sliced onions in an even layer on the bottom. Combine the onions with the Dijon mustard, minced garlic, and fresh thyme.

4. Carefully place the seasoned pork shoulder on top of the onion mixture.

5. Pour the apple cider and apple cider vinegar around the sides of the pork, being careful not to disturb the seasoning.

6. Cover the slow cooker and set it to cook on low for 8 to 10 hours, or on high for 5 to 6 hours, until the pork is fork-tender and easily shreds.

7. Once the pork is cooked, remove it from the slow cooker and use two forks to shred the meat, discarding any twine or bones.

8. Return the shredded pork to the slow cooker and stir it into the flavorful cooking juices. Serve warm.