The Hydrolysis Assisted Solidification (HAS) process was used in the slurry forming of Si3N4 green bodies. AlN powder was added to a highly loaded aqueous Si3N4 Slurry; which also contained Y2O3, prior to shaping by casting into a preheated impermeable mould. In order to preserve the reactivity of the AlN powder with water in the aqueous slurry, which is exploited for solidification in the HAS process, the concentration of the dissolved silica in the Si3N4 slurry was reduced by leaching the, as-received Si3N4 Powder before the slurry preparation. With leached Si3N4 powder, green bodies were successfully produced which were subsequently sintered to a high density. During AlN hydrolysis, a strong aluminum hydroxide network was formed resulting in dried green bodies with high strength. Alumina formed after the thermal decomposition of AI(OH)(3) later on served as the second sintering additive together with Y2O3, Microstructural characteristics and the mechanical properties of HAS-formed and sintered Si3N4 ceramics did not differ from those obtained with conventionally shaped material.