they build them up in layers, thermosetting resin IIRC, UV-cured, and it may need a bunch of sanding and painting to look nice.  this may be more a japanese speciality.  try one about 30 - 40 cm in height.  there may be a formulaic requirement in relation to pj's advice to avoid any limbs crossing each other or any part of the body, e.g. the distinction between a function and a relation, but I dunno how to convey it in terms appropriate to this forum.  they should be able to work around the problem of an hand or elbow starting in mid-air with some creative use of linking bars, as they do when casting plastic objects.  hence if anybody does one of these, let us see some photos of it.