Slice apples cross wise to about 1/8" thin with either a sharp knife or mandolin slicer.
Line some cookie sheets with parchment paper and arrange the slices on the cookie sheets making sure they do not overlap. Sprinkle with cinnamon if you like.
Bake the apple slices at 200 degrees F for 1-2 hours, checking after 45 minutes. You want these to be crispy, but not burnt. After 1 hour, check every 30 minutes. If some slices get crispier sooner, remove them from the pan first while the others dry more
Once the apple chips are dry enough, set them on a cooling rack to cool.
Allow to cool completely before storing in a sealed container for up to 7 days. Enjoy!
If your kids are a bit picky about the center of the apple chips, you can core the apple first and then slice them.