  Using a Monte Carlo random walks of a log-normal distribution, we show how to
qualitatively study void properties for non-standard cosmologies. We apply this
method to an f(R) modified gravity model and recover the N-body simulation
results of (Achitouv et al. 2016) for the void profiles and their deviation
from GR. This method can potentially be extended to study other properties of
the large scale structures such as the abundance of voids or overdense
environments. We also introduce a new way to identify voids in the cosmic web,
using only a few measurements of the density fluctuations around random
positions. This algorithm allows to select voids with specific profiles and
radii. As a consequence, we can target classes of voids with higher differences
between f(R) and standard gravity void profiles. Finally we apply our void
criteria to galaxy mock catalogues and discuss how the flexibility of our void
finder can be used to reduce systematics errors when probing the growth rate in
the galaxy-void correlation function.
