Coat the insert of a 4-quart or larger slow cooker with butter. Melt the 4 tablespoons of butter in a large frying pan over medium heat. Add the corn and cook, stirring occasionally, until any liquid has almost evaporated, about 5 minutes.
Meanwhile, whisk the eggs, milk, cream, flour, sugar, and salt together in a large bowl until combined; set aside.
When the corn is ready, add it to the egg mixture and stir with a rubber spatula to combine. Scrape the mixture into the slow cooker and spread into an even layer.
Cover the slow cooker and cook until the pudding is just set, 2 to 3 hours on LOW depending on the size of the slow cooker. Start checking at 2 hours; the pudding is done when the middle is not liquid anymore, but wobbles gently like Jell-O. Serve immediately.