Cut each apple in half then slice each end of the apple (the stem and butt). Slice the remaining apple into approximately ⅜” thick slices, making the slices as evenly as possible. Use a mandolin if you have one. (Do not slice too thin or the apple will stick to the dehydrator.)
Repeat for the remaining apples. Place cut apples into the lemon water, stirring so each apple is coated with the water. Let soak for 8-12 minutes, stirring occasionally (this step is optional).
Preheat the oven to 200F. Line a baking sheet (or multiple large baking sheets) with parchment paper and place the apple slices in a single layer, without overcrowding them.
Bake the slices for 1 hour to 1 ½ hours. At the halfway mark, check the apples to ensure they’re cooking evenly, and rotate the baking sheet if necessary. Also, flip the apples over at this point.
Continue to bake the apples until they are crispy and all the moisture has evaporated. Store them in an airtight container in the pantry.
After soaking, place apples in a single layer on dehydrator trays.
Set the temperature to 145F and allow it to run for 8-12 hours, testing at the 8-hour mark for doneness.
Apples should be hard and crunchy without any moisture. Dehydrate apples longer if they are too chewy.