Apart from the relatively "fast" propagation through separation of the established plants from the mother plant, there is also the possibility (rather slow way...) to propagate Sansevierias through the leaves cuttings... In total it can take up to 2-3-4 years till your get a well established new plant, i.e. your patience is expected! Please note that e.g. the variegated crossings of S.trifasciata will always turn through the leaf cutting propagation to the basis green form.  I find it always pretty fascinating story to see how the plants slowly develop... What about you? Did you already propagate your Sansevierias through leaves cuttings?