This work proposes the use of the educational robot construction procedure towards the cultivation of spatial thinking as a cross-cutting thread in STEM education. The work builds upon the idea that spatial thinking is malleable and initially presents a theoretical background to build upon. Then, an empirical case on the construction procedure of a robot, by a pair of primary school students using WeDo 2.0 blocks, is presented and spatialized in terms of construction actions and relevant argumentation. This exemplar case is used for the realization of the possibilities that stem from this spatialization to promote spatial thinking. The proposed work contributes at the metacognitive level to promote possible far transfer of spatial thinking in STEM domains.