Firebricks

Nothing in this list is craftable in turn, so one Firebricks is a single step: 3 units of material drawn from 2 base items, plus 1 crystal.

That bill outweighs 3,373 of the 13,602 recipes tracked here and 426 of the 1,591 Alchemist ones, and 9,374 recipes nest deeper.

Both raw materials are gathered, and no spot for either is timed, so nothing in the tree waits on the Eorzean clock.

Firebricks is itself consumed by 27 further recipes, spanning three of the eight crafting classes.