K.G.3
Ask your child to find an example of a "flat" (2d) shape (a drawing of a sun might be a circle or a piece of paper might be a rectangle). Then ask your child to find an example of a "solid" (3d) shape (a tissue box might be a cube, a ball would be a sphere). They don't need to know the vocabulary (cube, sphere, etc.), they just need to be able to identify whether shapes are flat or solid.