A flexible mat forming system may include an elongate, rotatable drum having a plurality of transverse rows of mold cavities about an outer periphery thereof, an elongate hopper positioned adjacent the drum, the hopper shaped to receive a hardenable paste and deposit the hardenable paste along a facing row of the plurality of transverse rows of mold cavities, a spool assembly for feeding a sheet of mesh material between the hopper and the facing row, and a retaining plate extending partially about the outer periphery of the drum and positioned on a downstream side of the elongate hopper, the retaining plate spaced sufficiently close to the outer periphery to retain the mesh material against the outer periphery of the drum and the hardenable paste within the mold cavities adjacent the retaining plate.