A modular flow platform for natural product synthesis was designed. To access different reaction setups with a maximum of flexibility, interchangeable 3D-printed components serve as backbone. By switching from liquid- to gas-driven flow, reagent and solvent waste is minimized, which translates into an advantageous sustainability profile. To enable inert conditions, “Schlenk-in-flow” techniques for the safe handling of oxygen- and moisture sensitive reagents were developed. Adopting these techniques, reproducible transformations in natural product synthesis were achieved.