Preheat the oven: Set your oven to 225°F (110°C). Line two baking sheets with parchment paper or silicone baking mats for easy cleanup.
Prep the apples: Rinse and dry the apples.
You can leave the skins on for color and extra fiber. Core the apples if you prefer, or leave the cores for a pretty star pattern in the middle.
Slice thinly: Using a sharp knife or a mandoline, slice the apples crosswise into very thin rounds—about 1/16 to 1/8 inch thick. The thinner the slices, the crisper the chips.
Optional lemon bath: If using lemon juice, mix it with a cup of water in a bowl.
Dip the slices briefly, then pat them dry. This step helps keep the color bright.
Season: Arrange slices in a single layer on the prepared sheets. Mix the cinnamon, sugar (if using), and a tiny pinch of salt.
Lightly sprinkle over the slices. Flip and dust the other side if you like extra flavor.
Bake low and slow: Place both sheets in the oven. Bake for 45 minutes, then rotate the pans and flip the slices.
Bake another 30–45 minutes, or until the chips feel dry and edges curl slightly.
Check doneness: Chips should feel firm and mostly dry. They will crisp more as they cool. If some slices are thicker, leave them in a bit longer while removing thinner ones.
Cool completely: Turn off the oven, crack the door open, and let the chips cool inside for 10–15 minutes.
Transfer to a rack to cool fully. This helps lock in crunch.
Taste and store: Once cool, taste one. If it’s still a little chewy, pop the batch back in the warm oven for 10–15 minutes.
Store only when fully cool.