Press the garlic or mash it. Pour all of the spices, garlic and oil at the bottom of the plastic bag. Add the chopped potatoes as well.
Squeeze the opening of the bag tightly with your fingers, so the spices don't spill out, and shake the bag energetically for 2 to 3 min. until all the potatoes are well covered in the spice mixture.
Arrange the potatoes in a flat oven dish covered with baking paper, without overlapping them or having any of them over one another.
Bake in a preheated 482°F (250°C) oven for about 20 min. or until crispy in appearance.
Salt them after you take them out of the oven.