  We describe how NNLO final state quark-pair corrections are computed in FDR
by directly enforcing gauge invariance and unitarity in the definition of the
regularized divergent integrals. The whole procedure is strictly
four-dimensional and renormalization is performed by simply fixing bare
parameters in terms of physical measurements. We give details of our approach
and demonstrate how virtual and real contributions can be merged together
without relying on dimensional regularization. As an example, we recompute the
${ H} \to b \bar b + {jets}$ and $\gamma^\ast \to {jets}$ inclusive rates at
the NNLO accuracy in the large $N_F$ limit of QCD.
