We study the $Z_{cs}\left(3985\right)$ and $Z_{cs}\left(4000\right)$ exotic states in the decays of ${\Lambda }_b$ baryons through a molecular scenario. In the final state interaction, the ${\Lambda }_b\to {\Lambda }_c^{+}{D}_s^{(⁎)-}$ decays are followed by the ${\Lambda }_c^{+}{D}_s^{(⁎)-}$ to $Z_{cs}^{-}p$ rescatterings via exchange of a $D^{(⁎)}$ meson. We predict a branching fraction of $\left({3.1}_{-2.6}^{+1.4}\right)\times {10}^{-4}$ for ${\Lambda }_b\to Z_{cs}^{-}p$, which can be measured in the ${\Lambda }_b\to J/\psi K^{(⁎)-}p$ decay. This study proposes a new approach to test the molecular model, and guides future experimental searches for the $Z_{cs}\left(3985\right)$ and $Z_{cs}\left(4000\right)$.