Provided is a levelling spacer device for laying slab products for cladding laying surfaces. In some embodiments, the levelling spacer device includes a support having a base and a separator element provided with a through-window with two upper tilted sub-edges and a lower edge; and a presser wedge to be inserted in the through-window and to slide restingly on the in-view surface of the slab products, with an upper face having two adjacent areas running longitudinally along the length of the pressing wedge, and that are tilted downwards towards each other along a common convergent axis, and that cooperate, each, with a respective one of the two upper tilted sub-edges to push the slab products downwards. Also provided is a computer program product for manufacturing the presently disclosed device by 3D printing.