Preheat the grill to 390°F (200°C) for 15 minutes.
Scrub and wash the potatoes, and pat them dry with paper towels.
Pierce the potatoes with a fork a couple of times on each side to allow heat to escape.
Brush the potatoes with any neutral oil that has a high smoke point (such as avocado or grapeseed oil), and season with sea salt.
Wrap each potato individually in 2 layers of foil.
Place the wrapped in foil potatoes directly on the grill, and cover with the lid. Cook for 45-55 minutes turning halfway through, or until you can easily pierce the center of a potato with a knife or a fork. If you have a kitchen thermometer, the internal temperature should be around 205°F (95°C).
Using kitchen tongs, remove the hot potatoes from the grill and allow them to cool down a little so that you can handle them with your hands.
Unwrap foil, and cut the potatoes open immediately with a knife as otherwise they'll steam inside and become heavy.
Add a piece of butter, and lightly fluff with a fork then serve with your favorite toppings!
Select starchy potatoes for the best results. If you're in the UK go for Maris Piper or King Edwards. If you're in the US, go for Russet potatoes. Choose potatoes that are similar in size to get even cooking.
If you have a kitchen thermometer, the internal temperature should be around 200-210F (93-100C).
If you have leftovers, store in the fridge for up to 3 days and reheat in the microwave, oven, or air fryer.