Mix together sugar and cornstarch in the saucepan. Use a wooden spoon to stir in the corn syrup, glycerin, water, butter, and salt. Place the saucepan over medium heat (7/10) and stir until the sugar dissolves. Continue stirring until mixture begins to boil, then let cook, undisturbed, until it reaches about 270° F or the soft-crack stage. Wash down the sides of the pan with a pastry brush dipped in warm water while the syrup cooks. Remove the saucepan from the heat and add food coloring and flavoring, as well as the baking soda. Stir gently, then pour onto a greased marble slab or into a shallow greased cookie sheet to cool. When the taffy is cool enough to handle, grease your hands or gloves with oil or butter and pull the taffy until it's light in color and has a satiny gloss. The glycerin helps add that shine. You can have a friend help with this step (or a hanger, chair, and duct tape), which should take about 10 minutes. Pull off sections of the taffy to work with individually to roll. Then roll the pulled taffy into a long rope, about 1/2 inch in diameter, and cut it with greased scissors or a butter knife into 1-inch-long pieces. Let the pieces sit for about half an hour before wrapping them in wax paper or plastic wrap and twisting the ends of the wrapper. Devour!