Bad Piggies Ground Hog Day Level 1-15 is 3-starred in two steps. Build a vertical contraption with the tnt and wood frame, lining up the soda bottles on each side. Navigate the pig very high by triggering the soda first and by detonating the tnt when it nears the star box. Then modify your setup by removing the tnt box, as it is a forbidden part, and adjust the soda bottles so that the contraption is sent flying directly towards the finish line.
If you have a different strategy for completing this level feel free to leave a comment below.