Whisk the rice flour, cornstarch, tapioca flour, baking powder, baking soda, xanthan gum, and salt together in a bowl; set aside. Grease a baking sheet, or cover with a sheet of parchment paper.
Beat the shortening and sugar with an electric mixer in a large bowl until light and fluffy.
Pour in the flour mixture alternately with the milk, mixing until just incorporated. Drop onto the prepared baking sheet into 8 equal portions.
Bake in the preheated oven until golden brown on the bottoms, 10 to 12 minutes.
Remove, and cool on a wire rack to room temperature.
Once cool, slice each shortcake in half, and place each bottom half onto a dessert plate. Evenly divide the sliced strawberries onto each shortcake, and dollop with the whipped topping.
