I use an inexpensive OXO Good Grips Hand-Held Mandoline Slicer
(affiliate link) that has 3 settings. I recommend slicing apples on the number 2 setting for crisp apple chips. I found that my lowest setting made the apple slices too thin. For a more chewy apple chip I recommend slicing the apples on the third setting. You may core your apples, but I choose not too. In my opinion I think the center star shape is very attractive and natural looking. Although, I do remove the seeds and remove the centers as needed. No worries, some apple slices may not be perfect. The apples chips maybe slightly moist when first taken out of the oven, but will crisp as they cool. Leave apple chips on baking sheet as they cool. Please double the recipe as needed :)