Preheat your oven to 225 degrees Fahrenheit. Line two large baking sheets with parchment paper or silicone baking mats. It's possible that not all of the chips will fit on two baking sheets at once, you can work in batches if necessary.
Combine white sugar, cinnamon, and nutmeg in a bowl, stir until the cinnamon is evenly distributed.
Grab your mandolin and thinly slice your apples on the second-to-smallest setting. There's no need to core them, though if you really want to, you can. You want each slice to have uniform thickness, which is why we recommend a mandolin as opposed to hand chopping.
Lay apple slices in a single layer on your baking sheets. Sprinkle each side of the chips with the cinnamon sugar mixture.
Bake for 1 hour. When the initial hour is finished, flip the apple chips and bake for another hour. Depending on your oven, keep an eye on your apple chips in the last 10 minutes of baking to make sure they don't burn.
Let cool on a wire rack, and store in a sealed container.