Use a roll of paper, or attach multiple pieces of large paper together. Trace the child's body, as he lays on top of the paper. He can use multicolored markers to draw the details of his own body. He can also use construction paper to cut out clothing and internal body parts.
Learn about the inner body parts by creating costumes that feature those organs right where they actually lie. For example, attach pictures of hand bones to gloves. Create a headband with a picture of a brain. Make a vest with a heart, lungs, stomach and intestines. Layer parts if necessary.
Use pre-cut or pre-drawn body or head shapes. Have children look in a mirror and draw what they see on those shapes. Purchase them in different shades of brown, or have the children use multicolored markers to show their colors.