In essence he began with a rectangle, about 11" x 14", of a clear gelatin-like sheet. This was the surface on which he would make his art. He rolled out some ink onto this surface until it was coated. Then he scraped away ink with various tools to create designs. When he was ready, he lay a piece of paper down onto the top of that surface. Voila! When he lifted it, the paper had a design on it.
Here are a few images from that demo, to see how it was done.
The Gelli (small version)
Prints he made by painting on this, scraping away some of the paint, and then pressing a piece of paper down onto that surface.
He also does other styles of printmaking.
Woodblock, i.e. carving a design into wood.
Collagraph, i.e. pasting / layering items onto a cardboard rectangle and then using that as a stamp.
Lithograph, i.e. drawing on limestone with crayon so you get a raised design. Now you can use that as a stamp.
For even more photos:
Randy LeSage Demo at BVAA Website
Printmaking Basics and Tips - main page