CR 8? (Slightly better than a flesh golem)
Here's an attempt at construction...
The pieces of a necromantic golem must come from normal human corpses that have not decayed significantly. Assembly requires a minimum of ten different bodies. The corpses must be stripped of their flesh and the bones, which are then rendered in two vats. The resulting semi-liquid bone-paste is then cast into a new articulated skeleton, to which the rendered flesh is applied like wet clay to shape the figure. Special unguents and bindings worth 1,000 gp are also required. Note that creating a necromantic golem requires casting a spell with the evil descriptor.
Assembling the body requires a DC 15 Craft (sculpting) check. Alternatively, special vats may be designed with a DC 20 Knowledge (architecture and engineering) check. These vats may be used to create additional necromantic golems, provided the other prereqs are met.
CL 8th; Craft Construct, animate dead, death ward, geas/quest, limited wish, caster must be at least 8th level; Price 25,000 gp; Cost 13,500 gp + 960 XP.