I started the lesson by sharing a couple diagrams of bodies and we looked at how parts measured up to each other and the whole body too. Then we drew a practice body (mannequin style) to get a feel for how to measure these parts and put them together. We also drew a target. Both drawings were then shaded to turn them into 3d solids. We then added a a couple details to the target to make it seem like we were looking at it from above.
Their job, then, was to create a winter scene that included a body making a snow angel, a snowperson, and at least 2 other setting details. Each thing in the drawing needed to be shaded or colored light to dark, to make them seem 3d.
Last year as 3rd graders, these kids made lego self portraits and they had to use light and dark to make them look 3d. I allowed students to use mini-figs as their subject as long as they still could demonstrate an understanding of proportion verbally and on their exit slips.