This site is in Japanese but has been translated to English.
What is BJD you ask!
The following description of a BJD was taken from the Noah's Doll tutorial:
It is a kind of a doll with ball-and-socket joints in its body, arms and legs. Limbs and head are joined together by loops of elastic. There are many variations in the way to join each part of a doll.
Arms are attached by elastic running through the armholes and torso.
Each leg has its own piece of elastic. Loops of elastic run from the ankle up through the knee, through the leg-hole and up to the head. Both loops being hung on a hook inside the neck.
Other ends of the elastic are attached to small "S" shaped hooks inside the wrists and ankles respectively.
If constructed properly and is well-balanced, a BJD can stand on its own.
Of course, to have this type of joint stringing, the doll must be hollow. There are several different methods for accomplishing this. Noah's doll uses a combination of Styroform, sawdust clay and stone clay (LaDoll). All air-dry products.
If sawdust clay is not available to you, Celluclay (an instant papier mache pulp) or an air-dry clay such as Paperclay could possibly be substituted for constructing the base form over the Styrofoam. Do not use polymer clay for base layer because the Styrofoam armature CANNOT be placed in oven.
Hope you enjoy this tutorial and try making your own BJD. For future reference, I will be adding this tutorial to my Air Dry Clay Tutorial Directory.