Add the lemon juice to the bowl of water. Set aside. Preheat your oven to 225 degrees with the rack in the center of the oven.
Peel one apple, remove the core. From the top, cut the apple in half then slice off the top and bottom ends to create an even starting point for slicing. Slice the two halves into thin slices. As thin as possible! Place the slices inside the bowl of water with the fresh lemon juice as you go.
Spread them out onto a cookie sheet and set them aside to air dry for an hour. If you can put them near a window with a lot of sunlight, that would be best. After an hour, flip them onto the other side. Let them air dry another hour.
Bake the apple slices for 45 minutes. After 45 minutes, remove them from the oven and flip the slices over once more. Bake another 45 minutes.