Combine the oats, milk, and desired add-ins in a spacious glass container and stir thoroughly until the mixture is fully blended. Cover securely with a lid or plastic wrap and refrigerate for at least two hours, preferably overnight, to allow the oats to soak. Incorporate toppings either before chilling or immediately prior to serving. When ready to eat, remove the cover and enjoy directly from the container, thinning with additional milk or water if a looser consistency is preferred.