The method is very simple, you draw a simple shape using straight lines that encompass the object(s) you are drawing. This helps to simplify things and to see the big shapes, and trains you to look for the big shapes before the small ones.
For example, in Bouguereau's Virgin of the Angels, the envelope would look like this, something like a slanted diamond:
image from the J. Paul Getty Museum |
Here is a picture of some of the pieces from my student art show. All the pieces on the far right panel are of grade school students' work, ranging from 2nd to 8th grade, and I taught all of them this method. The pencil portrait of Abraham Lincoln was done by one of my 5th grade students and it won first place in the Thinkin' Lincoln Art Contest.