To sign rice, form your dominant hand into the ASL letter R sign. Then we create a bowl with our non-dominant hand, while making a spoon with the 'R' formed by the dominant hand. We spoon the rice all the way to our mouth. (Note that we sign soup with a very similar sign, except we use a curved U hand for the "soup spoon".)
We teach rice when we introduce our babies to this type of food.
Food items are helpful in empowering our babies to communicate their food preferences. Use rice contextually during meals.