Using the serrated knife, cut the 2-inch plastic foam ball in half. Use one half for the body; set the other half aside for a future project. Dab crafts glue on one end of two toothpicks; insert the glued ends into the bottom of the body, leaving 1-1/2 inches of the toothpicks extended for legs.
Cut two 2-inch lengths of florist's wire. Bend each wire into a V shape for an arm. Dab glue onto both ends of each arm, and insert the ends into the sides of the body.
For the neck/head armature, dab glue onto one end of a toothpick. Push the glued end into the top of the body, leaving about 1 inch extending from the top.
Push a thin paintbrush handle halfway into the 1-1/2-inch plastic foam ball for the head. Attach the plastic foam ball head to the neck/head toothpick with glue, tilting the head at an angle. Set the completed armature aside until glue dries.
Sculpt the body:
Note: Keep a small bowl of warm water handy to moisten your fingers and tools as you sculpt the shape.
Roll out a generous handful of the Paperclay. Using your fingers, water, and the flat paintbrush, smooth the Paperclay over the armature until it is completely covered, building up layers and thickness until the desired shape is achieved.
For the hands and feet: Press pea-size balls of Paperclay into mitten and boot shapes.
For the sleeve and leg cuffs: Roll out a thin 1-inch-diameter circle of clay, then cut it into four narrow strips using the crafts knife. Wrap the strips around the wrists and ankles. Add texture to the cuffs with the end of a toothpick or paintbrush handle.
For the collar: Roll out a thin 1/2-inch-wide strip of clay long enough to wrap around the neck. Round the ends and press the collar in place.
For the buttons: Roll three tiny balls of clay, and press them to the body.
Sculpt the head:
Apply a smooth layer of Paperclay over the head. Form two pea-size balls of Paperclay for cheeks and one small cone shape for a nose.
Flatten the cheek balls into puffy pancakelike shapes and attach them to the head, smoothing them in place with a paintbrush and water.
Shape the cone into a nose and attach it to the head. Create nostrils with a toothpick.
For the beard: Roll out a thin 2-inch-diameter circle of Paperclay; cut out a 2-inch-long crescent shape about 1/2 inch wide at the center. Shape and press it to fit under the nose and around the chin. Add texture to the beard with a toothpick.
For the mustache: Roll out a 2-inch-long snakelike shape and cut it in half. Referring to the photo, coil one end of each half. Press the mustache pieces over the beard and add texture with a toothpick.
For eyebrows: Roll out a 3/4-inch-long snakelike shape and cut it in half. Press the eyebrows to the forehead and add texture with a toothpick.
For the mouth: Add a pea-size ball of Paperclay under the mustache. Use a toothpick to create an opening and to draw ends of the mouth into a smile.
For the hat: Roll out a 1/2-inch-wide cone shape with an extra-long tip. Referring to the photo, roll the tip into a tight coil. Press the hat in place.
For the hatband: Roll out a snakelike shape about 3 inches long. Wrap and attach hatband around hat. Add texture with the end of a paintbrush.
Let the sculpture dry for several days.
Paint and antique the santa:
Base-coat entire sculpture with gesso. Referring to the photo, paint Santa and the papier-mache box. For uniform polka dots, dip the eraser end of a new pencil into paint and press dots onto Santa's suit and hat.
When the paint is dry, cover Santa and the box with clear matte finish. Let dry.
To create an aged patina, mix 1 part burnt umber paint to 3 parts water. Brush mixture over Santa and the box. Quickly wipe away excess mixture with paper towels, allowing mixture to remain in indented areas; let dry.
Finish the sculpture:
Glue Santa to the box. Prop figure on the box or hold it in place until it is dry enough to stand on its own.
Brush glue over Santa's collar and the box lid and sprinkle with clear-glass glitter.