The generation of diffractive optical elements often requires time and cost consuming production techniques such as photolithography. Especially in research and development, small series of diffractive microstructures are needed and flexible and cost effective fabrication techniques are desirable to enable the fabrication of versatile optical elements on a short time scale. In this work, we introduce a novel process chain for fabrication of diffractive optical elements in various polymers. It is based on a maskless lithography process step, where a computer generated image of the optical element is projected via a digital mirror device and a microscope setup onto a silicon wafer coated with photosensitive resist. In addition, a stitching process allows us to microstructure a large area on the wafer. After development, a soft stamp of the microstructure is made from Polydimethylsiloxane, which is used as a mold for the subsequent hot embossing process, where the final diffractive optical element is replicated into thermoplastic polymer. Experimental results are presented, which demonstrate the applicability of the process.