This paper describes an intuitive method for the design and fabrication of small-scale robots with multi-material compliant mechanisms in 3D. The rigid components are 3D printed, and flexures are inserted into the rigid components, creating the final mechanism. The assembled mechanisms are robust, requiring over 1 N of force to delaminate, and surviving 150,000 cycles of bending without failure. A 6 g walking quadrupedal millirobot is presented as a case study for the design and manufacturing methodology. The quadrupedal millirobot has been demonstrated moving at top speeds of 9 mm/s (0.3 body lengths/s).