Preheat oven to 250°F. Line two baking sheets with parchment paper.
Core apples and slice into thin rounds or half-moons. Place in a bowl and toss with cinnamon until evenly coated.
Lay apple slices in a single layer on prepared baking sheets.
Place in the oven and bake for 30 minutes, then flip slices and return to the oven for another 30 minutes. Check for crispness, then continue cooking in 15-30 minute increments, until dried to your liking.
Let cool completely (apples will dry further as they cool). Store in an airtight container at room temperature for up to 1 week.