Spray a baking sheet with non-stick baking spray; set aside.
Slice potato lengthwise into ¼” slices. Lay each slice flat and slice into ¼” strips. After slicing, rinse potatoes in cold water. Pat fries lightly with paper towel to remove excess water.
Place fries, oil and seasonings in a large plastic bag; shake until fries are well coated.
Arrange fries in a single layer on prepared baking sheet.
Bake for 24-30 minutes, or until edges of the fries turn golden brown.
Notes
Depending on the size of your potatoes, you may need to cut the oil, rosemary, salt and garlic back. I found these proportions worked well for the size of potatoes that I used, though.