Mathematicians have already proved the possibility of making 3D objects from a ribbon. You can see how to make a tetrahedron in Figure 1. The ribbon is folded according to the drawn lines, sides of equilateral triangles.

One can make a cube using a similar way (see Fig. 2). Its faces are lined up in a chain, and in order to change the direction of the ribbon to complete the formation, it is enough just to fold it on the diagonal of the square (the article about a cube made of ribbon was published in “Science and Life”, №10, 1972)