With the help of a prepared cake, this dessert is a snap to assemble; be sure to allow enough time for it to firm up in the freezer.
Split cake in thirds horizontally using a serrated knife; place bottom cake layer, cut side up, on a platter. Arrange 1/2 cup strawberries on cake; spread with 1 1/2 cups yogurt, and top with middle cake layer. Repeat the procedure with 1/2 cup strawberries and 1 1/2 cups yogurt. Top with remaining cake layer; freeze 2 hours.
Combine 1 cup strawberries, sugar, and orange juice in a blender, and process until smooth. Cover and chill. Serve sauce with cake.