Identify shapes as two-dimensional (lying in a plane, "flat") or three-dimensional ("solid").
Identify two- and three-dimensional shapes. Cut-outs of shapes and physical blocks to start. Then identify from pictures of shapes and solids. The student doesn’t know about planes, so the term “plane figure” and the phrase “lying in the plane,” won’t be introduced here.
Notes: The Common Core sometimes mentions how to represent concepts, and in other cases, does not. I find this inconsistent and annoying.