A hot-forming die has a heatable lower die and a heatable upper die. The lower die and the upper die have spacer elements to permit flexing. A plate stack including two plate elements is inside the hot-forming die. The plate stack is on the spacer elements in the lower die. The lower die and the upper die are displaced relative to each other when the hot-forming die is closed. The spacer elements of the upper die come into contact with the plate stack. As the closing movement continues, the spacer elements, are displaced into the lower die and the upper die, respectively, and the plate stack is clamped between the lower die and the upper die. The plate stack is then heated by the lower die and the upper die and an internal pressure is applied to an intermediate space between the plate elements by feeding in an active medium.