In a small saucepan off heat, combine the rice flour, sugar, and salt until well mixed. Add 1⁄4 cup of almond milk and place the saucepan over medium-low heat, mixing well to dissolve the rice flour and sugar.
Add the remaining almond milk, stirring constantly until mixture thickens for about 3 minutes.
Remove the pan from heat and whisk in the dairy-free margarine and vanilla until completely incorporated.
Transfer pudding to heatproof bowl or serving dishes, place plastic wrap directly on the surface of the pudding and chill in the refrigerator for at least 3 hours before serving.
Serve cold with a dollop of dairy-free whipped topping.