Wash debris off potatoes. Pat dry. Get out a piece of foil for each potato that is large enough to wrap around each one entirely.
Lay each one in the middle. Lightly drizzle a bit of olive oil on each potato with a sprinkle of salt.
Roll each one up in the piece of foil with the ends folded over so it is secured. Lay inside slow cooker overlapping the least amount possible.
Close lid and set to low setting for 4-5 hours. Timing will depend on their size, test tenderness by sticking a knife into the center. When it slides in easily they are done.
If you want the skins crispy, preheat air fryer to 400 degrees F. Spray the skin all over with olive oil and set inside basket without overlapping for 4-6 minutes turning over once. Remove once skins are as crispy as you'd like them to be.