Preheat the oven to 200ºF / 90ºC and line 2 large baking trays with parchment paper.
Slice the apples very finely and lay them on the baking trays in a single layer.
Transfer the trays into the oven and bake until the apples become crisp – about 1 ½ to 2 hours. When ready leave the apples to cool on the tray before transferring them to a container and eat them within a week.
Note: you can do the same with bananas too but keep in mind that bananas will take around 30 min more of baking, depending on their thickness.
