Cook the potatoes in a microwave for about 10 to 15 minutes, a little under fork tender. They don't have to be cooked all the way. Allow to cool and then peel and slice thinly.

Set a saucepan over medium heat and add the butter. Once melted, stir in the flour and cook for about 30 seconds. Slowly stream in the milk, while whisking. Cook on low until thick along with the garlic and thyme. Season with 1/2 teaspoon salt and 1/2 teaspoon black pepper. Once thick, remove from heat, discard the thyme and garlic and stir in the cheese (reserving some for the top).

Pour half the sauce into the bottom of your slow-cooker. Top with potato slices and season with remaining 1 teaspoon salt and 1 teaspoon black pepper. Pour the remaining sauce and sprinkle with reserved cheese.

Place the lid on and cook on low for about 6 to 8 hours or on high for 3 to 4. Sprinkle with fresh thyme on top and serve immediately.