Step 1: Select your materials
Step 2: Make attachment points in the chunks of material
Step 3: Assemble the sculpture
Draw the secret shape you are making on a piece of paper, and tape that paper to the wall. While you are assembling, you will be constantly holding up the sculpture at arm's length and viewing against the template on the wall. then bend any piece which is out of position to fit the template.
Wear latex gloves to keep fingerprints off the pieces, otherwise you will need to clean afterwards with alcohol.
After assembly, I put a little glue on a lot of the connections to prevent shifting. Or, you could dip the entire thing in paint.