Add the sliced onions and minced garlic to the bottom of the slow cooker and spread them into an even layer.
Place the pork chops on top of the onions in a single layer.
Sprinkle the thyme, salt, and black pepper over the pork chops.
Pour the apple cider over everything, making sure it covers most of the meat.
Cover and cook on low for 6 to 7 hours until the pork is tender.
Remove the pork chops and set them aside on a plate.
Stir the cornstarch and water together in a small bowl, then add the mixture to the slow cooker.
Stir the sauce and cook on high for 15 minutes until it thickens slightly.
Return the pork chops to the slow cooker and turn them to coat in the sauce before serving.