I don't know about a formal instruction per se, but maybe this will help. Use a 12" X 12" piece of plywood or fiberboard for the base. For the spine, I nail a length of 1" X 2" furring strip (wood) to the center of one edge so it sticks straight up. Tightly roll/twist some newspaper, using shipping tape to keep it twisted. These will be the ribs. I used a staple gun to attach them to the furring strip. Bend them into a rib cage shape and tape them together at the sternum. I used a thicker paper roll for the shoulders. Here's a pic to show you what I mean.
HalloweenGallery.com - Halloween 2007/DSC03563ss
After that, start applying the mache. I start with paper towel strips dipped in a 50/50 water and white glue mix. I usually use thick napkins to finish the "skin" - you can make lots of interesting wrinkles with that stuff, and it dries hard and rigid.
I used a plastic skull model for the head. Wrap the skull in foil then apply a few layers of paper towels/glue mix. When dry, cut it up the back to remove it from the model. Close the slit with tape and more mache. Attach the skull in the appropriate place and apply mache as you see fit.
On the groundbreaker in the pic, I used a gel wood stain as the base coat and dripped diluted black acrylic paint into the creases in the skin to give more definition. Have fun!
