Mold free and additive embedding of quasi-spatial filter (QSF) for simple optical detection was proposed. With a concept of “silicone optical technology (SOT)” we proposed, fully flexible and digitally fabrication of compact optical module for flow-injection analysis (FIA) was demonstrated. It was attained by combining silicone 3D printed rough-frame and injecting and coating method for embedding SOT-QSF that can trap unexpected light signal as tilted incidence. SOT-QSF’s coaxial cylindrical structure of PDMS core and carbon-dispersed-PDMS clad was fabricated by injecting and coating method. The coating properties and optical trapping performance was evaluated. These embedding techniques and method developments will be useful for on-site applications with general FIA researches and for rapid on-demand-fabrication based on researcher’s idea.