You have learned or should learn an earlier basic tutorial on describing shapes, understanding the use of perspective and reference point.
Now these videos show you how to describe shapes and their sizes, using facial grammar, specifically mouth movements: "mm" for medium, "oo" for small and tiny, and "cha" for huge.
These three mouth movements (mouth morphemes) are general but there are "gradiations" by inflecting these mouth movements. For example, adding intensity to these mouth movements mean tiny or very-small or very-huge. Squinting eyes with "oo" mouth movement signifies very-small or tiny.
Practice on your own before looking at the answer below each video clip. Get your paper and pen ready. Play the video and watch. Write or draw down. Repeat the video if necessary. Compare your answer. One at a time. If necessary, adjust or resize your browser to cover the answer below the video.
Use puffy cheeks to represent a shape of the blob.
Also see describing shapes and locations (beginning).