Start out with a medium-size square of tinfoil, placing the potato square in the middle. Puncture the skin several times with a fork, then lightly coat with olive oil. Sprinkle on a bit of salt, then wrap it up.
Repeat the process for as many potatoes you like, depending on how big your slow cooker is. Switch it on and leave to cook for 6-7 hours at low, or 4-5 hours at high. Once unwrapped, these potatoes will be tender, fluffy and absolutely delicious.