Impact of the survey mask. Top: Estimated skewness in the three geometries from the COVMOS simulations (light coloured plain lines) and the Gaussian field realisations, where the contribution from IC is not subtracted (dotted lines). We also show our empirical model for the Gaussian field without the IC contribution (dark coloured solid lines). Bottom: Difference between the skewness estimated in the COVMOS simulations and the Gaussian realisations with and without IC (light coloured plain and dotted lines, respectively).