A method for creating a platform cooling passage in a turbine rotor blade, wherein the turbine rotor blade comprises a platform at an interface between an airfoil and a root, wherein the platform includes a platform topside along an outboard surface, the method comprising the steps of: forming a recessed area along the platform topside; forming a coverplate; and affixing the coverplate to the platform topside; the coverplate being configured to correspond to the shape of the recessed area such that, when affixed to the platform topside in a desired manner, the coverplate substantially encloses the recessed area to form the platform cooling passage therein; the method further comprising the steps of: forming an inlet through which, in operation, coolant enters the platform cooling passage; forming an outlet through which, in operation, coolant exits the platform cooling passage; and forming fluid directing structure within the platform cooling passage; wherein: once the coverplate is affixed to the platform topside, an outer radial surface of the platform within the platform cooling passage area comprises a floor of the platform cooling passage, and the inner radial surface of the coverplate comprises a ceiling of the platform cooling passage; the fluid directing structure comprises wall-partitions that extend substantially from the floor to the ceiling of the platform cooling passage; and the wall-partitions are configured to define a winding path through the platform cooling passage, the winding path configured to fluidly connecting the inlet to the outlet. forming a recessed area along the platform topside; forming a coverplate; and affixing the coverplate to the platform topside; the coverplate being configured to correspond to the shape of the recessed area such that, when affixed to the platform topside in a desired manner, the coverplate substantially encloses the recessed area to form the platform cooling passage therein; the method further comprising the steps of: forming an inlet through which, in operation, coolant enters the platform cooling passage; forming an outlet through which, in operation, coolant exits the platform cooling passage; and forming fluid directing structure within the platform cooling passage; wherein: once the coverplate is affixed to the platform topside, an outer radial surface of the platform within the platform cooling passage area comprises a floor of the platform cooling passage, and the inner radial surface of the coverplate comprises a ceiling of the platform cooling passage; the fluid directing structure comprises wall-partitions that extend substantially from the floor to the ceiling of the platform cooling passage; and the wall-partitions are configured to define a winding path through the platform cooling passage, the winding path configured to fluidly connecting the inlet to the outlet. forming an inlet through which, in operation, coolant enters the platform cooling passage; forming an outlet through which, in operation, coolant exits the platform cooling passage; and forming fluid directing structure within the platform cooling passage; wherein: once the coverplate is affixed to the platform topside, an outer radial surface of the platform within the platform cooling passage area comprises a floor of the platform cooling passage, and the inner radial surface of the coverplate comprises a ceiling of the platform cooling passage; the fluid directing structure comprises wall-partitions that extend substantially from the floor to the ceiling of the platform cooling passage; and the wall-partitions are configured to define a winding path through the platform cooling passage, the winding path configured to fluidly connecting the inlet to the outlet.