Complex sentence: They must attach a handle, choosing from a range of provided materials; grind, sharpen, and polish the blades; and address any flaws or issues pointed out by the judges in the first round, if they choose to do so.
Split into simpler sentences: They must attach a handle (choosing from a range of provided materials), grind, sharpen, and polish the blades. They can also address any flaws or issues pointed out by the judges in the first round, if they choose to do so.