The combination of the nonsolvent-induced phase separation (NIPS) process with a solvent vapor annealing (SVA) treatment is used to produce asymmetric and hydrophobic thick films having different long-range ordered network nanostructures, which are inaccessible via currently available membrane fabrication methods. We show that the disordered phase generated by NIPS on the material top surface can be transformed into a highly ordered bicontinuous network nanostructure during the SVA process without disrupting the substructure morphology. For instance, by using a straightforward blending approach, either a triply periodic alternating diamond (D-A) structure or a core-shell perforated lamellar (PL) phase was demonstrated on the skin layer of fully hydrophobic poly(1,1-dimethyl silacyclobutane)-block-polystyrene-block-poly(methyl methacrylate) (PDMSB-b-PS-b-PMMA) thick films. Such a material fabrication method, enabling the formation of a sponge-like substructure topped by a network phase having an excellent long-range order, provides an appealing strategy to facilitate the manufacture of next-generation membranes at large scale since these bicontinuous morphologies obviate the need of the nanochannel alignment.