The correct way to dry apples is wash them, remove soft spots, skin them (optional), and dry them. It's possible to use a food dehydrator, an oven or a car to dry the apples.
Select the healthiest apples, and clean in cold plain water. Some elect to remove the skin at this stage, and a mechanical peeler and corer is the most efficient way to do this. Then, core and slice the apples into small pieces. If you wish to add spices, do so now. Place them in the dryer. The setting and the drying time varies depending on the type of dryer and moisture content of the apples.