Preheat oven to 300 degrees F. Spread bread cubes in two 15x10-inch baking pans. Bake 10 to 15 minutes or until dry, stirring twice. Cool. (Or let bread cubes stand, loosely covered, at room temperature for 8 to 10 hours.)
Line a 3 1/2- or 4-quart oval slow cooker with a disposable slow cooker liner; coat liner with cooking spray. Place bread cubes in prepared cooker.
In a large bowl whisk together the next six ingredients (through salt); pour over bread cubes. Use a large spoon to press bread down slightly to moisten. Cover and chill 4 to 24 hours.
Cover and cook on low about 3 hours or until a knife comes out clean, giving crockery liner a half-turn halfway through cooking, if possible. Turn off cooker. If possible, remove crockery liner from cooker. Let stand, covered, 30 minutes. Serve with maple syrup.