  The interfacial free energy between a crystal and a fluid, {\gamma} cf, is a
highly relevant parameter in phenomena such as wetting or crystal nucleation
and growth. Due to the difficulty of measuring {\gamma} cf experimentally,
computer simulations are often used to study the crystal-fluid interface. Here,
we present a novel simulation methodology for the calculation of {\gamma} cf .
The methodology consists in using a mold composed of potential energy wells to
induce the formation of a crystal slab in the fluid at coexistence conditions.
This induction is done along a reversible pathway along which the free energy
difference between the initial and the final states is obtained by means of
thermodynamic integration. The structure of the mold is given by that of the
crystal lattice planes, which allows to easily obtain the free energy for
different crystal orientations. The method is validated by calculating {\gamma}
cf for previously studied systems, namely, the hard spheres and the
Lennard-Jones systems. Our results for the latter show that the method is
accurate enough to deal with the anisotropy of {\gamma} cf with respect to the
crystal orientation. We also calculate {\gamma} cf for a recently proposed
continuous version of the hard sphere potential and obtain the same {\gamma} cf
as for the pure hard sphere system. The method can be implemented both in Monte
Carlo and Molecular Dynamics. In fact, we show that it can be easily used in
combination with the popular Molecular Dynamics package GROMACS.
