The picture I saw is at this blog: http://artinthestudio.blogspot.com/2010/10/anna-hepler.html which explains a process that is complicated and I don't have the same tools that the artist did. Not to be deterred I decided to try it differently and the result is something wall-worthy
Step 1: Materials
Sun Art paper - 7 pieces of 4"x6" 4 pieces form the main picture for the top and 3 form the design on the sides.
Mod Podge (or similar glue)
Set of 4; 4"x4"x1 1/2" canvas (I used a 4 from a pack of 9 from Michaels which means I can create another whole set with a square for another project!)
tape to make the sculpture: I used scotch for this because it's translucent which is key in getting shadows with light was well as sturdy enough to hold a 3D shape. If you used a core of a thin strip of scotch I think that regular clear tape would work. Also, a turns out a plastic bottle ring (the stuff that comes on 8 pack of soda) could work too if you don't want to sculpt your own
Shallow tub with water to set the paper.
Step 2: Creating the Sculpture
The pattern I followed involved taping 3 different length pieces together into a circle with 2 twists. Then I took a 2 more lengths of tape and connected 2 seams on the initial circle. Continue taping various length pieces starting and ending on seams. You will also need some "support strips" that join the middle loops. These will begin and end on the loops instead of seams. The "support strips" can be much smaller and are to keep your sculpture actually 3 dimensional.
If you're using the soda rings, you can skip this step as your sculpture essentially exists. I'd pull one end of the rings through a hole on the other side in an attempt to make it 3d.
Also experiment with turning the sculpture in different directions. One side could be better than another.
Step 3: Assemble Paper
The other 3 pages are for the sides so they don't have to be taped together but they also will be getting the shadow treatment.
Step 4: Cast Shadows
You'll want to take your paper out and expose to the sun with the sculpture on top for about 1-3 minutes, depending on the amount of light and the density of your sculpture. I set the ones that I made for 1 minute. I'm also impatient.
The biggest thing to look out for is wind. You don't want wind to move the sculpture while you're trying to get the shadow. You can lightly tape it to the paper to prevent total movement, but you might then get the shadow f the tape because it's not 100% clear. Aim for a day/time with little to no wind.
At this point you want the sculpture for the main picture and you can cast the sides with something else. It's important to do the sides because with 1" sticking off the wall, you'll definitely still see them. You don't have to be as careful because you're only seeing an inch at a time so just any shadow pattern works.
Step 5: Set Shadows
The colors come out while the paper is drying so don't worry if your paper looks like it's "wrong". The magic of chemistry ordains that the colors will switch and become much more vibrant after setting.
Take out of the water and let dry on a paper towel. This might take some time. You paper might also crinkle. If it crinkles, flatten between some books before continuing.
Step 6: Create the Main Picture
Step 7: Finish Sides
Finish by applying a new layer of mod podge to seal everything as well as add a shiny finish.