In a large skillet cook bacon until crisp; transfer to paper towels to drain. Reserve half the bacon. In a 4- to 5-qt. slow cooker add remaining bacon, potatoes, juice from the clams (reserve clams), onion, garlic, bay leaves, salt, and pepper. Cover and cook on low 5 to 6 hours or high 2 1/2 to 3 hours. Refrigerate bacon and clams until ready to use. In a small bowl, whisk together the half-and-half, milk, flour, and butter. Allow to stand at room temperature 30 minutes. If using low heat, turn to high. Gently stir milk mixture into the slow cooker. Cover and cook 30 to 40 minutes more or until thickened and bubbly. Gently stir in reserved clams. Turn cooker off. Cover and let stand 10 minutes. Remove and discard bay leaves. Top servings with reserved bacon, crackers, and thyme if desired.