An improved process to make a slurry catalyst for the upgrade of heavy oil feedstock is provided. In the process, at least a metal precursor feedstock is portioned and fed in any of the stages: the promotion stage; the sulfidation stage; or the transformation stage of a water-based catalyst precursor to a slurry catalyst. In one embodiment, the promoter metal precursor feedstock is split into portions, the first portion is for the sulfiding step, the second portion is for the promotion step; and optionally the third portion is to be added to the transformation step in the mixing of the sulfided promoted catalyst precursor with a hydrocarbon diluent to form the slurry catalyst. In another embodiment, the Primary metal precursor feedstock is split into portions.