Just one seat back could be removed. They just bolt in and hinge forward. The rear seat cushion is one piece.
One a side note removing the rear seat cushion is how the fuel pump assembly is accessed. Under the rear seat cushion is a plate covering a hole in chassis. Removing this plate exposes the top of the fuel tank and the wiring and fuel pump assembly. The fuel is lifted from the tank and removed through the vehicle. No more f$!#ing around under the vehicle and dropping the tank.
One of better enerineering solutions over the years.
2014 Fiesta Titanium Hatch, 5-speed, Performance Blue