Preheat your grill to medium-high heat (around 375-400°F/190-204℃).
Cut both ends off the plantain with a sharp knife. This makes it easier to peel. Slice a shallow slit down the long seam of the plantain, and peel only as deep as the peel. Remove the peel by pulling it back.
Slice plantains in half lengthwise into 2-3 pieces depending on the size of the plantain.
Brush both sides of the plantain slices with melted coconut oil, ensuring they are evenly coated.
Place the plantain slices on the preheated grill. Cook for 2-3 minutes (until they are lightly browned and have grill marks). Flip the plantains carefully using a spatula and let them grill for another 2-3 minutes or more until done.
Once the plantains are grilled to your preference, remove them from the grill and let them cool for a few minutes.
Transfer the grilled plantains to a serving platter or individual plates.