You can slice them very thinly and then cook them on a low heat in the oven, but be warned that they won't be sin-free if you do this. The reason being that many sin-free foods are sin free because they fill you up and are low in calories. If you change the way it is cooked so that they no longer fill you up, then you are likely to end up eating a whole lot more calories without it filling you up. same as lasagne doritos and baked chick peas etc.
Shame as they're so nice!
Oh and they're also labour intensive if you make them this way - they shrivel up to nothing, so what was a full baking tray only has a handful of crisps after an hour or so of cooking!