Pull the skin off and slice in 1/2-inch rounds. If it is a really big plantain you'll get about 16-18 slices.
Soak for a few minutes in cold salted water and then pat dry before you drop them in hot oil. Turn when just golden.
Remove, absorb excess oil on kitchen paper and then smash them with a rolling pin or a press (you don't want to destroy the slices, just flatten them).
Then drop them in hot oil again and fry until golden.
Remove and place on kitchen paper once more. This time they will be fantastically crispy.
Sprinkle with salt. They deserve to be eaten while still warm.
Serve with a sprinkling of minced garlic in oil if you like.