Methods for manufacturing a wind turbine rotor blade having a flatback airfoil configuration along at least a portion of a span of the rotor blade include providing a shell mold of the rotor blade. The method also includes laying up an outer skin layer of the rotor blade into the shell mold. Further, the method includes placing at least one pre-fabricated corner of the flatback airfoil configuration into the shell mold. The pre-fabricated corner(s) has a pointed edge. The method also includes infusing the outer skin layer with the pre-fabricated corner(s) to form the flatback airfoil configuration.