Lightly grease a 6-quart slow cooker. Peel the potatoes if desired and cut them into even 1/2-inch cubes.
Add the potatoes to the slow cooker, followed by the frozen corn, diced onion, and minced garlic.
Sprinkle in the thyme, garlic powder, salt, and pepper. Pour in the chicken broth and stir gently.
Cover and cook on Low for 6 to 7 hours or High for 3 to 4 hours, until the potatoes are fork-tender.
Mash a portion of the cooked potatoes directly in the slow cooker, leaving plenty of chunks.
Melt the butter in a small saucepan over medium heat. Whisk in the flour and cook for 1 minute, stirring constantly.
Slowly whisk in the heavy cream and cook gently for a few minutes until smooth and slightly thickened.
Stir the cream mixture into the slow cooker. Cover and cook on Low for another 20 to 30 minutes, until hot and creamy. Taste, adjust the seasoning, and serve warm.