Application-specific network-oriented communication architectures have recently become an effective solution to support high bandwidth Systems on-Chip. The Network on-Chip architectures considered so far range from regular to fully customized topologies for application-specific designs requiring high-level bandwidth. To this end, a network-centric design flow is necessary to support the design space exploration of complex SoCs with tight design constraints. This paper introduces four different approaches based on the orthogonalization of core mapping and topology customization applied to STNoC, the Network on-Chip developed by STMicroelecronics. The four methods are derived from the combination of the initial mappings to two standard topologies (ring and spidergon) with two types of topology customization based on the insertion of cross-links to reduce the network distance of standard topologies.