A modular wind turbine assembly platform (WTAP) comprises a crane module and at least one work module for temporary storage of wind turbine components, and a modular floating hull assembly platform (FHAP) comprises a crane module and at least one work module for temporary storage of floating platform hull components and a large floating mat, wherein each of the modules comprises a rectangular hull and a plurality of retractable legs with each leg featuring a large-size footing in a water depth of 5 to 15 meters. A method for assembly of a floating offshore wind turbine comprises a floating wind assembly base (FWAB) including the modular FHAP and WTAP deployed at a near-shore site within a distance of 200 to 2000 meters from a shoreline. The method further comprises assembling a floating platform hull and lowering it into the water using the FHAP with the floating mat, then assembling and integrating a wind turbine with the floating platform hull using the WTAP.