Bad Piggies Rise and Swine Level 2-9 can be 3-starred in one step. Build a four frame vehicle, place the engine in the back, and freckles in the front with a boxing glove behind him pointing up. Navigate your vehicle all the way around the cave, trigger the boxing glove when it reaches the star box. Then continue navigating, and stop when your vehicle is above the finish line.
If you have a different strategy for completing this level feel free to leave a comment below.