I’m unfamiliar with Rice Milk. Boil some rice?
I do not know how it gets in the container at the health food store. I think it's "magic."
I do make my own almond milk though, and it's way incredible. Place fresh raw almonds in water and soak them for a "spell." Then blend them (1 cup to 4 cups water) at high speed. Strain that glop in cheesecloth, throw the milk portion back in the blender, add some agave, almond extract, pinch of salt, and it's a glutton's dream. Love the stuff. Keeps me in the Confessional. :)