Preheat the oven to 425 F (218 C) and line a large baking sheet with parchment paper.
To cut the plantains, trim and discard the ends. Then use the tip of your knife to make a shallow cut lengthwise through the peel, doing your best not to pierce the flesh of the plantain. Remove the peel and slice the plantain on an angle into 1/4-inch slices.
Place the sliced plantains on the prepared baking sheet and toss with oil and salt (optional).
Bake for 10 minutes, then flip and bake for another 5-10 minutes or until golden brown and slightly caramelized on both sides.