I first use one of my favorite gadgets. An apple peeler slicer. I love this thing. It peels, slices, and cores your apple all with a few quick cranks of the handle.
Then put in a container with a lid and let sit overnight. This is the conditioning process. It allows the moisture to evenly distribute through the fruit. As long as there is not moisture on the lid of the container the next morning your apples are properly dried.