The strategy for Hammerfest Level 13, Big Finish, is to drop the long slap to create a catapult and bring the Viking down next. For a 3-cut par, simply drop a large chunk of ice onto the right end of the catapult. For the treasure chest, make your first cut above and a second cut below the chest. Note that the second cut occurs while the slab is falling, so don’t hesitate!
If you have a different strategy for completing this level feel free to leave a comment below.