Method for producing a vanity unit assembly, in which: - a cutout is made in a receiving surface comprising a thick layer of a support material covered on at least one face with a thin layer of laminated material, named the laminated layer, said cutout being made in the support material according to a contour of a basin and leaving a border of the laminated layer overhanging toward the inside of the cutout, - an injection mold is used, comprising two parts of complementary shape, a first part, named the concave shell, comprising at least one recessed part suitable for forming a convex outer surface of the basin and a second part, named the convex shell suitable for forming a concave inner surface of the basin, said mold being adapted to receive and clamp the receiving surface between the two shells, the laminated layer of the receiving surface facing the convex shell, characterized in that: - a preform of the basin is made from a thin sheet of thermoplastic synthetic material(s), named the decorative film, the preform comprising a planar rim along its contour, toward the outside of the preform, said rim having a width smaller than the width of the border of the laminated layer, - the preform and the receiving surface are installed in the mold in the following order: concave shell, preform, receiving surface, convex shell, so that the preform is inserted into the cutout formed in the support material and that the planar rim of the preform comes into contact with the border of the laminated layer, - the mold is closed and a second thermoplastic synthetic material, named the injected material, is injected between the concave shell and the preform. - a cutout is made in a receiving surface comprising a thick layer of a support material covered on at least one face with a thin layer of laminated material, named the laminated layer, said cutout being made in the support material according to a contour of a basin and leaving a border of the laminated layer overhanging toward the inside of the cutout, - an injection mold is used, comprising two parts of complementary shape, a first part, named the concave shell, comprising at least one recessed part suitable for forming a convex outer surface of the basin and a second part, named the convex shell suitable for forming a concave inner surface of the basin, said mold being adapted to receive and clamp the receiving surface between the two shells, the laminated layer of the receiving surface facing the convex shell, - a preform of the basin is made from a thin sheet of thermoplastic synthetic material(s), named the decorative film, the preform comprising a planar rim along its contour, toward the outside of the preform, said rim having a width smaller than the width of the border of the laminated layer, - the preform and the receiving surface are installed in the mold in the following order: concave shell, preform, receiving surface, convex shell, so that the preform is inserted into the cutout formed in the support material and that the planar rim of the preform comes into contact with the border of the laminated layer, - the mold is closed and a second thermoplastic synthetic material, named the injected material, is injected between the concave shell and the preform.