Construction processes, particularly floor slab systems, can be executed using precast/precast methods as technology advances. Compared to traditional methods, which need more time and production expenses, precast/precast methods are more cost-effective for floor slab formwork, neater, and have a more consistent finish. This study is based on an eight-floor building project with 92 residential units on a 3,500 m2 plot of land and a 1,700 m2 building size. This investigation used two technologies: conventional precast slab and full slab precast. The purpose of this research is to compare the most cost-effective strategy for reducing production costs on floor slab work for the construction of the case study. Based on the calculation results, the full slab precast method is 14.31% or around Rp. 980,508,000 is more economical than the conventional method. For the conventional method, the total cost is Rp. 3,914,657,000 while for the precast method, the result is Rp. 2,934,149,000.