  We show that a qubit transfer protocol can be realized through a flat band
hosted by a disordered $XX$ spin-1/2 diamond chain. In the absence of disorder,
the transmission becomes impossible due to the compact localized states forming
the flat band. When off-diagonal disorder is considered, the degeneracy of the
band is preserved but the associated states are no longer confined to the unit
cells. By perturbatively coupling the sender and receiver to the flat band, we
derive a general effective Hamiltonian resembling a star network model with two
hubs. The effective couplings correspond to wavefunctions associated with the
flat-band modes. Specific relationships between these parameters define the
quality of the quantum-state transfer which, in turn, are related to the degree
of localization in the flat band. Our findings establish a framework for
further studies of flat bands in the context of quantum communication.
