To kick off my afternoon class which focused on famous artworks from the 20th century, we studied Piet Mondrian. After viewing lots of his artwork (and seeing his influence on pop culture with the Partridge Family bus) the kids set to work drawing a minimum of 4 vertical lines, 4 horizontal lines, and 3-5 partial lines either direction, first with a pencil then just beside their lead line they drew another line this time with sharpie. This left double lines that they'd later paint in.
Lastly they made their black lines thinker with paint, filling in those gaps we left earlier.
Several of them said that this was a lot harder than it looked!