Stepladder

Taken all the way down to base materials, one Stepladder is 3 crafting steps deep and needs 3 intermediates — Walnut Lumber ×5, Steel Ingot ×3 and Steel Rivets ×2 — which resolve to 3 distinct raw materials totalling 24 units, plus 28 crystals.

That bill outweighs 8,926 of the 13,602 recipes tracked here and 904 of the 1,552 Carpenter ones, and 337 recipes nest deeper.

Only 6 of those crystals go into the final step; the other 22 are burned by the intermediates, so the real crystal cost is 13 Wind Shard, 12 Fire Shard and 3 Ice Shard.

The chain crosses two disciplines — Carpenter to Lv 30 and Blacksmith to Lv 29 — so no single class can finish it unaided.

All 3 raw materials are gathered, and not one of their spots is timed, so nothing in the tree waits on the Eorzean clock.

Of the intermediates, Walnut Lumber has the widest use: 128 recipes call for it, spanning eight of the eight crafting classes.