There is provided a method and network management function for allocating a slice instance of a communications network. The method includes obtaining, by a management function, requirements for the slice instance and checking, by the management function, a feasibility of the slice instance requirements in view of one or more of network resources and network capabilities. The method further includes preparing, by the management function, a network environment for the slice instance in view of the slice instance requirements and commissioning, by the management function, the slice instance. The method may additionally or alternatively include terminating, modifying and/or deactivating the slice instance.