Lightly butter the slow cooker bowl. Add the rice, milk, sugar, vanilla, salt and diced butter. Stir well.

Grate nutmeg over the top, cover and cook on low for 3-4 hours, stirring once or twice, until the rice is tender and the mixture is thick and creamy.

Let the pudding sit for 5-10 minutes off the heat before serving to reach its final creamy consistency.