Preheat oven to 200° F. Line two baking sheets with parchment paper or silicone mats.
In a small bowl, combine the oil and all flavour drops. Set aside.
Using a mandolin, carefully slice the apples into approximately 1/8-inch thick rounds. Alternatively, you can use a sharp knife to slice the apples as thinly as possible (if using a knife you will need to bake the longer as they will be thicker).
Arrange the apple slices in a single layer on the baking sheets. Remove any seeds.
Use a pastry brush to lightly brush on the flavoured oil. Lightly sprinkle over some salt.
Bake for 1 hour. Flip and bake for an additional 1- 1 1/2 hours. To determine when the chips are ready, remove one from the oven and let it sit at room temperature for 5 minutes. If it becomes crispy, they are ready. If not, continue baking in 15-minutes increments. The total cooking time and the final colour of the apple chips will be dependent on the moisture level of the apples you choose.
Once done, turn off the oven but let the apple chips cool in the oven for an additional 30 minutes to ensure any remaining moisture is cooked out.
Remove from the oven. Once fully cooled, store in an airtight container for up to 1 week.