To make beetroot chips, peel and thinly slice the beet, using knife and chopping board or using a mandolin slicer.
Toss the slices in oil and 3-4 pinches of salt.
Preheat the airfryer for 3-4 minutes at 200xb0C.
Open the basket of the airfryer and slide in the beetroot slices. Shake the basket to spread the slices out (no need for them to be in a single layer).
Slide the basket back into the slot and bake / airfry at 200C for 12-18 minutes. This depends on the thickness of your slices. Make sure to pull out the basket and give it a good shake 2-3 times during the whole process, so all of them get uniformly crisp.
The chips will turn really crisp on cooling, so take care not to burn them by keeping it for too long.
Remove the chips in to a dish. Allow to cool for 5-7 minutes and then serve immediately. Sprinkle some sea salt if you like, just before serving.
To make these beetroot chips in a regular convection oven, preheat the oven at 180xb0C before slicing the beets. Follow steps 1 and 2. Layer the chips in a single layer in two baking sheets (or more) and bake for 15 minutes. Keep a watch so they don't burn.