Abstract This paper presents a novel design methodology for automatically constructing soft robots with modular, LEGO‐like origami actuators. By assembling these modular soft actuators, intricate robotic systems can be created. The key innovation of the work lies in the incorporation of thickness accommodation into kinematics models and the optimization‐based assembly strategy standardizing the design process. This approach has been validated through two LEGO‐like origami actuators, which are then assembled guided by the assembly strategy. A robot arm built by these actuators showcased a remarkable position accuracy, deviating by only 3 mm at the tip over a 400 mm span. Furthermore, two soft robots are successfully designed, built, and tested for manipulation and tight space inspection, and a bipedal walking robot, confirming the feasibility of the design algorithm for functional robotic systems. This work offers a comprehensive design framework that standardizes the assembly of LEGO‐like origami actuators into accurate and functional robotic systems.