Scrub each potato thoroughly under cold running water, removing any eyes or blemishes. Pat completely dry with paper towels. Pierce each potato 8-10 times with a fork, creating deep holes that prevent bursting and allow steam to escape during cooking.

Rub each potato with olive oil, ensuring the entire surface is coated. Sprinkle generously with coarse salt and pepper, pressing gently so the seasonings adhere.

Place seasoned potatoes directly in your slow cooker – no water needed. Cover and cook on LOW for 3-4 hours for medium potatoes, or up to 5 hours for extra-large ones. You'll know they're ready when a fork slides through easily and the skin feels slightly crispy when tapped.

Using tongs, carefully remove hot potatoes. Make a deep lengthwise cut, then gently squeeze both ends toward the center. The fluffy interior should burst open like a flower. Fluff the flesh with a fork, creating pockets for toppings.

Add a pat of butter to each potato, letting it melt into the warm flesh. Top with sour cream, shredded cheese, and fresh green onions. The residual heat will melt the cheese perfectly.