This paper presents the development of a multimodal, automated fabrication approach for a modular, material-efficient reinforced concrete slab system. The proposed concept combines 3D concrete printing (3DCP), robotic casting, and the automated integration of tailored preformed carbon fiber-reinforced polymer (CFRP) reinforcement profiles. The individual slab modules, consisting of thin plates and ribbed substructures, are manufactured in a continuous, digitally controlled process and assembled using demountable dry joint connections with external post-tensioning. To achieve the smooth and geometrically precise surfaces required for these connections, the modules are post-processed by robotic milling. Experimental investigations on bond, bending, shear, punching, and the load transfer in the dry joint connection demonstrate the structural feasibility of the system and highlight the influence of reinforcement configuration and fabrication parameters. The results show that the multimodal approach enables the production of modules with high load-bearing capacity while significantly reducing material usage compared to conventional slab systems. The presented methodology contributes to the development of scalable approaches for the industrial production of adaptive and resource-efficient ribbed reinforced concrete members.