Spray 5-quart slow cooker with cooking spray. Place bread and raisins in slow cooker.
In a medium bowl, whisk together milk, eggs, sugar, melted butter, cinnamon, vanilla, nutmeg and salt. Pour mixture over bread. Toss to evenly coat bread. Let sit 10 minutes then toss again to evenly distribute custard.
Cover and cook on low heat for 2 hours and 30 minutes, or until knife inserted comes out clean. Serve warm topped with whipped cream. Enjoy!