Energy-harvesting technologies offer a sustainable, maintenance-free alternative to conventional energy-storage solutions in distributed low-power applications. Flexible thermoelectric generators (TEGs) can generate electric power from a temperature gradient, even on complex surfaces. Organic materials are ideal candidates for flexible TEGs due to their good solution-processability, natural abundance, low weight, and flexibility. Electronic and thermoelectric properties of organic materials have steadily progressed, while device architectures leveraging their advantages are largely missing. Here, a design and fabrication method are proposed for producing fully screen-printed, flexible monolithic organic TEGs scalable up to m², compatible with any screen-printable ink. This approach is validated, along with its scalability, by printing TEGs composed of two different active inks, in three configurations, with up to 800 thermoelements, with performances well matching simulations based on materials parameters. It is demonstrated that by using an additive-free graphene ink, a remarkable power density of 15 nW cm⁻² at ΔT = 29.5 K can be achieved, with an estimated weight-normalized power output of 1 µW g⁻¹, highlighting a strong potential in portability. Owing to such power density, only limited areas are required to generate microwatts, sufficient for operating low-power electronic devices such as sensors, and wearables.