Cuttings can work but are the least successful method. Species clematis, like SAC (not evergreen, btw) can be propagated from seed relatively easily but will take from 3-5 years to achieve flowering size. Large flowering hybrids can also be seed propagated but with no guarantee that the offspring will duplicate the appearance of the parent.

The most foolproof method is layering - easily done and pretty fast to accomplish and will be a clonal duplicate of the parent plant.