County of Fortune how to unlock building slots: supply the settlement with equipment. Give it one piece of equipment — a wooden chest or a wool tunic — and the second building slot opens; give it both and the third opens. You do it in the Needs tab, under Equipment.

County of Fortune how to unlock building slots: supply equipment

  1. Open the settlement and go to the Needs tab.
  2. Find the Equipment section.
  3. Pick the item — a wooden chest or a wool tunic — and let the settlement accept it.
  4. Open the Buildings tab. The extra slot is now there.
Equipment suppliedBuildings the settlement can run
None1 (the building you founded the settlement with)
One type of equipment2
Both equipment types3

At maximum level a settlement has three slots for each of the four social classes, twelve buildings in total. The freed slot can start a new resource or add a second copy of an existing building if your mayor's bonus points at that industry. Where the chests and tunics themselves come from is covered by production chains.

Equipment is also the population lever

Equipment does more than unlock slots. Supplying more equipment to a settlement also raises the maximum number of workers its buildings can hold, so equipment is the lever for population as well as for capacity. Population covers the other two levers, and production chains covers where the chests and tunics actually come from.