A method for forming complex-shaped sanitary fittings with a mold (10) that includes four parts (11, 12, 13, 14) made of porous resin capable of mutually self-centering by means of complementarily shaped locators (15), in which the method includes the following steps: (a) closing the mold by means of a manual or robotized handling device (23) that has a relatively low force; (b) inserting the closed mold inside a container (16) that has a relatively high force, and generating pressure on six faces of the mold (10); (c) injecting a slip inside the mold (10); (d) extracting the closed mold from the container (16); (e) opening the mold (10). The invention also relates to a device which includes: a container (16) that is suitable to generate pressure on six faces of the mold (10), and a conveyor means (22) for transferring the closed mold (10) inside the container (16).