I just toss both in a little bit of olive oil and sprinkle with sea salt. The sweet potato chips bake at 400 degrees until they're crispy. A mandolin slicer has been my best friend making these. I've experimented with different thicknesses and cooking times since buying it, and 1/16" for about 21 minutes is the winner in my book! I flip them with a fork halfway through.
The kale chips bake at 300 degrees for about 12 minutes. You really need to watch them closely though. There is a fine line for them between crispy and burnt. I've found you don't need to flip these and the fresher the kale, the better they come out!
My biggest problem? I can't make a batch of either without eating the whole pan of them as soon as they come out of the oven!