A flexible mapping method to map a Physical Coding Sublayer (PCS) structure from Flexible Ethernet and/or Multi Link Gearbox (MLG) to Optical Transport Network (OTN), includes receiving one or more Virtual Lanes; and mapping each of the one or more Virtual Lanes into a Tributary Slot, wherein a rate and number of the Tributary Slot(s) in OTN is set based on a rate and number of the one or more Virtual Lanes. A transport system and a flexible de-mapping method are also described. The systems and methods map the generalized MLG-style group of lanes (virtual PHYs/PMDs) into an OPUflex Tributary Slot (TS) structure, keeping PCS structures intact, and creates a single ODUflex container with a matching rate of FlexE for end-to-end flow.