My pictures are done with ink pens on archival paper. Most of the time, like with this picture, I simply start making dots and let them go where they will. I sometimes sketch out the image in pencil before beginning and then erase the pencil after I have captured the image in ink.
The originals generally are 8.5"x11". It takes anywhere from a few thousand to over 1 million dots (an average of 100 dots per minute) to fill a page.