Preheat oven to 400 degrees and prepare a baking sheet with parchement paper or avsilicone mat.
Slice the sweeet potatoes and put them in a bowl with the oil and spices. Mix well with your hands so that everything is well covered.
Arrange potato slices on a tray try to not overlap.
Put in the oven for ten minutes then rotate the trays and leave for 5 extra minutes.
Remove from oven and let cool.