Scrub 4–6 Russet or Yukon Gold potatoes under running water and pat them dry with a towel.

Tear off a piece of aluminum foil large enough to wrap one potato. Place one potato on the foil, drizzle it with olive oil, and sprinkle with kosher salt. Wrap the potato tightly in the foil. Repeat so each potato is individually wrapped.

Make 4–6 balls of aluminum foil about the size of a tennis ball (aim for one ball per potato) and arrange them in a single layer on the bottom of the slow cooker insert.

Place the foil-wrapped potatoes on top of the foil balls in the slow cooker in a single layer. Close the lid.

Cook on HIGH for 4 hours or on LOW for 6–8 hours.

Test a potato for doneness by piercing through the foil with a fork or skewer; it should slide in easily. If not done, continue cooking and recheck as needed.

When potatoes are cooked, turn the slow cooker to WARM if not serving immediately. Use tongs or oven mitts to remove the hot, foil-wrapped potatoes, unwrap, and serve.