Z-complementary code sets (ZCCS) are used in multicarrier code-division multiple access (MC-CDMA) systems, where they guarantee error-free transmission in a nonsynchronous setting. There aren't many direct ways to build binary optimal ZCCSs with lengths that are non-power-oftwo (NPT). This letter suggests two direct ways to build binary optimal ZCCSs with lengths that are NPT. The proposed designs are based on generalised Boolean functions (GBF). The results are new and does not exists in the literature.