Scatter half of the onion and apple slices in the bottom of a slow cooker.

Cut slits about every inch in the pork loin.

Stuff slits with apple and onion slices.

Set pork loin in slow cooker on top of onion and apple slices.

Season meat generously with salt and pepper.

Pour apple cider around meat in slow cooker.

Cook on High 5-6 hours or Low 8-10 hours.

Leaving slow cooker on, remove pork loin to platter to rest.

With a cooking spoon or ladle, dip out about 1/2 cup of juices from the slow cooker to a jar or plastic container with a lid.

Add corn starch to hot cooking liquid you removed.

Add lid to container of cornstarch and cooking liquid. Shake until cornstarch is dissolved.

Add cornstarch mixture back into slow cooker and stir to combine with other juices.

Let simmer in slow cooker for 15-20 minutes until gravy has thickened.

Shred pork.

Serve with some of the cooked apples and onions and gravy.