Heat olive oil in a skillet over medium-high heat.
Season the pork shoulder with salt and pepper and sear on all sides until browned, about 4–5 minutes per side.
Transfer the seared pork to the slow cooker.
In the same skillet, sauté minced garlic for 1 minute until fragrant.
Pour in apple cider and stir to combine with the garlic.
Pour the apple cider mixture over the pork in the slow cooker.
Add the sliced apples and cinnamon (either ground cinnamon or cinnamon sticks).
Cover and cook on low for 7–8 hours (preferred) or high for 4–5 hours until fork-tender.
Serve the pork with the apples and sauce from the slow cooker.