Making plantains is so easy it doesn't even require a recipe—it's all in the technique. I learned this one from my highschool best friend who's Puerto Rican. Akin to the double-fry method used for french fries, the slices are cooked in hot oil once until just before they become pale golden. I generally use canola oil since it's lighter and doesn't impart any flavor, but recently gave it a go with extra virgin oil and had equally delicious results.
They're then smashed thin using a tostonera (see pic 1). When I first started serving them up years ago, I'd use an empty wine bottle and give them a whack between two sheets of paper towels. Now I use the tostonera I got at the local Met Food for $2.
After you smash the plantains, fry them again for a couple of minutes on each side until they're deep golden and crisp. Drain on a paper towel-lined plate and season with salt. Serve hot.