The slices ideally are about 1/4 inch (1/2 cm) thick. If you do rings, you can run a string through them and hang them up in a cool place to dry out. It takes a few weeks and they will brown when drying.
Some people like to soak them first for 10 minutes in a week solution of ascorbic acid or lemon juice, to help minimize their browning. (Ascorbic acid is more effective.)
Sometimes the apple pieces are cut thicker, to make dried apple wedges and sometimes, the apple slices are dried in the oven instead, to make Oven-Dried Apple Chips, though this is very energy inefficient.
Dried apple heads, such as those used in crafts in making apple-head dolls, are made from whole apples. They are peeled, soaked in salt water for 1/2 an hour (to stop the apple from going a very dark brown), then carved to make the head, then propped up somewhere to dry.
You can also get freeze-dried apples.
Dried Apples are used in cooking, such as for pies and cakes. They are re-hydrated before use, usually by soaking overnight in water (some like juice instead.) Or, they may be simmered in water for 1/2 hour to 1 hour.
Per cup 6 oz (175 g) of Dried Apples, use 1 1/2 cups (12 oz / 350 ml) of water.
6 oz (175 g) Dried Apples = 1 cup = 2 2/3 cups re-hydrated.
8 oz (225 g) Freeze-Dried Apples = 8 cups apple pieces, re-hydrated.
Store Dried Apples in a covered container in a dark place.