I feel that this is the time to remind everyone that magic items do not exist by RAW, as their creation process is impossible.
Point 1, magic items are not able to be created without a magical formula for the item.
Point 2, a magical formula is a magic item one rarity higher than the item associated.
Point 3, Legendary magic items do not have magical formulas.
So, in order to create a magical formula, you need a formula for it one rarity higher, hence all require legendary formulas which cannot exist and cannot be created. As such, by RAW, magic items don't exist.