Melt the butter in a pan on low to medium-low heat. When it has completely melted, sprinkle in the rice flour in small handfuls. Stir and stir. When you have added all the flour and the mixture has become coherent (see picture above), let it cook in the pan for two to three minutes, stirring all the while. When it has cooked, it will be solidified and have a tinge of brown. Take the roux off the heat and let it rest for a moment. Put the roux back on low to medium heat. Slowly, in small amounts, add the chicken stock (or turkey juices), whisking the mixture vigorously until all the liquid has been absorbed in the roux. Continue to do this, in small drizzles, until the roux has expanded and liquified into gravy. This will take awhile, perhaps ten minutes or so. Be patient. When you have reached the consistency you desire for the gravy, add salt and pepper. Taste the gravy, and season according to your taste. Take it off the burner and serve it, immediately.