I would imagine you should use Piece by Piece (Armorer 50), Ingenuity II (Blacksmith 50) and do Standard Synthesis under Steady Hand I, restore Durability with either Master Mend I/II or Manipulation (Goldsmith 15) or Waste Not I/II (Leatherworker 15/50).
I know that for making 3 star food, I need Piece by Piece x2 + 3 Careful Synthesis II (Weaver 50) under the effect of Ingenuity II but the difficulty is probably not the same here.

Also try this.