Meso-membranes with highly ordered nanochannel arrays have been fabricated by patterning hexagonal boron nitride (h-BN) films using a focused ion beam. The complete experimental procedure is given in detail from the chemical vapor deposition for h-BN synthesis to its patterning and the final membrane design for nanofluidic experiments. The membranes obtained are characterized at each experimental step by electron microscopy and Raman spectroscopy. The technique is finally applied to fabricate devices in which the only passage for a fluid is a nanochannel array etched into a h-BN film.