The most basic and quick recipe I heard was after washing, toss with a little olive oil, put them on a cookie sheet in a single layer, sprinkle with salt and bake at 400°F for 5min*.
*ok, so this really, fast 5min cooking did not work, at least with our oven. In the end it took 25min before they were crisp
The chips were only o.k. partially because I skipped on the salt on half of them but honestly they need a little salt. The best was when my husband added his touch to the unsalted chips by sprinkling a bit of soy sauce, yum! The kids enjoyed them quite a bit but warning! they are super messy and crumble into tiny, green specks.
As I like to involve the kids in food prep as much as possible there contribution was to tear up the kale and they even instinctively knew to separate the leaves from the stems.