A food dish is not strictly necessary as most hamsters will be happy to eat from the floor of their cage and will often take food given on a dish to store elsewhere. Your hamster may also enjoy foraging for food in bedding. However, a dish can still be useful as it allows you to more easily measure servings of food and gives you a general idea of how much your hamster is eating.
If you do give your hamster a food dish then it is advisable to use a ceramic or metal dish rather than a plastic one so it cannot be chewed.