A plant for forming ceramic tiles or slabs comprising a conveyor belt (2) on which a continuous strip (100) of powdered ceramic material is created, compacting devices (4, 5) that allow said strip (100) of powders on the belt (2) to be subjected to continuous pressing to obtain a coherent article of compacted powders, and means that allow the lateral containment of the material on the belt, said means comprising at least one pair of parallel elastically deformable containment walls (8, 9), between which the powdered material is contained before, during and after pressing. Said containment walls (8, 9) have the interfacing sides (80, 90) inclined with respect to the plane of the conveyor belt (2), so that they do not interfere, after pressing, with the article of compacted powders, so as not to induce stresses in it that could cause it to be damaged.