DRAGON QUEST XI: Echoes of an Elusive Age

To unlock this trophy you need to successfully craft a +3 piece of equipment. There are two ways in which you can achieve this. While crafting an item from scratch if you do well enough in the forging mini game and manage to hit the "sweet spot" indicator on enough segments you will be awarded with a +3 piece of gear by default. You also have the option of reworking an already owned piece of gear enough times to upgrade it to a +3 version (see If At First You Don't Succeed for details on reworking items).

You don't really need to go out of your way to earn this. As your Hero levels up in the game so will your Fun-Size Forge which will unlock new skills and increase your Focus. By late game you will be making perfect items without even trying, especially if you are making a low level item.