Shield of Avon is crafted with Blacksmithing in Mabinogi (shield). This page lists everything needed to make it, checked against the game as it exists today. The interactive planner lives in the Blacksmith Companion.
How to get the manual
The manual is rank 3 and survives 30 uses; every crafting attempt spends one use.
G14: complete the Generation 14: Romeo and Juliet questline for the Shield of Avon blueprint. Generation 14: Romeo and Juliet; start after Generation 13 or at cumulative level 570 via Duncan.
Materials
Expect about 4 attempts per finished item (28% average progress per attempt). Per-attempt materials are consumed on every attempt; finishing materials once per item.
Each attempt uses
3× Iron Bar — refine from Iron Ingot via Blacksmithing (Refining)
3× Mythril Bar — craft via Blacksmithing from Mythril Ingot
3× Silver Bar — craft from Silver Ingot via Blacksmithing
1× Romeo and Juliet Script — Generation 14 story questline reward