Remove kale leaves from the woody stem, thoroughly wash and dry them and transfer into in a bowl.
Add the oil and some salt and massage the oil into the kale leaves so all the leaves are well coated.
Lay the kale leaves in a single layer on the baking tray with some space between them. You might need to bake them in more than 1 batch.
Bake for 10 -12 mins until crisp but not burnt making sure you turn them half way through baking. Do keep an eye on your kale crisps as they do burn rather quickly.
If you find that few leaves are not crispy then pick them out and put these back into the oven for a few minutes.
Notes
Try and make sure each baking try has leaves of similar sizes so that they all cook at the same rate.