The oxide-based garnet LLZO (Li7La3Zr2O12) is a promising ceramic separator material for solid-state batteries due to its relatively high ionic conductivity (10-4 – 10-3 mS cm-1), wide electrochemical stability window, stability against lithium metal, and processability in ambient atmosphere. Nevertheless, challenges associated with upscaling the manufacturing process must be addressed, such as reducing manufacturing costs and energy consumption, and optimizing the conditions for producing high-quality separators with a large geometry and an adjustable microstructure in a scalable process. To this end, we have identified two large-scale synthesis and processing techniques, namely spray drying and tape casting, as suitable industrially established methods for the simple and efficient production of LLZO separators with larger geometries (with a target of 5×5 cm²). While spray drying enables the large-scale synthesis of LLZO powders with optimized morphology, tape casting can be used for the continuous production of porous and dense LLZO separators in one or more steps. The multilayer electrolyte geometries enable optimal tortuosity while increasing the energy density and mechanical stability of the battery. This study focuses on the production of dense and porous single- and multilayer separators with flat and large geometries by optimizing parameters of spray drying, particle size and particle size distribution, slurry preparation and their rheology, and the sintering process to enable the large-scale production of flat, free-standing ceramic separators.