Papier mache is a great sculpting medium which became popular in the 1800s to make dolls. It is making a comeback now, partly because it is so durable, light, and easy to make. Pulp paper mache has several advantages over strip paper mache. You can sculpt with it, you don't have to dry it in layers as you do with strip paper mache, and you can use filler material to change the composition. Fillers can make the paper mache stronger or more interesting. For example, fillers can include saw dust or glitter. There are many recipes for paper mache pulp.
Make or find a box form. You can make a box out of foam core. Cut five congruent squares out of the foam core and Duct tape together to form a box. You can also use a plastic cube or plastic food container.
Make paper mache pulp. Tear cardboard egg cartons into large pieces. Soak the pieces in hot water overnight or for several hours. Break up the pieces with your hands, then transfer to a blender or food processor. You may want to use a separate blender or food processor just for crafts.
Drain out excess water. Transfer the pulp to a large bowl. If you have used a plastic form, apply a layer of vaseline to the form to help release the box after it has dried. Apply pulp to the box form, sculpting and forming the pulp into the exact shape you want. You can smooth the pulp to exactly match the box shape, or you can sculpt free form in any way you like.
Allow to dry in a place where air can circulate freely around the box. The drying time will vary depending on thickness of your project.
Remove from the form. Sand if desired. Paint with Gesso. Paint several layers of Gesso if you want a smooth, durable finish. Sand between coats for an even smoother finish.