3D microfluidic device fabrication methods are normally quite expensive and tedious. In this paper we present an easy and cheap alternative wherein thin cyclic olefin polymer (COP) sheets, and pressure sensitive adhesive (PSA) were used to fabricate hybrid 3D microfluidic structures, by the Origami technique, which enables the fabrication of microfluidic devices without the need of any alignment tool. The COP and PSA layers were both cut simultaneously using a portable, low cost plotter allowing for rapid prototyping of a large variety of designs in a single production step. The devices were then manually assembled using the origami technique by simply combining COP and PSA layers and mild pressure. This fast fabrication method was applied, as proof of concept, to the generation of a micromixer with a 3D stepped serpentine design made of 10 layers in less than 8 min. Moreover the micromixer was characterised as a function of its pressure failure, achieving pressures of up to 1000 mbar. This fabrication method is readily accessible across a large range of potential end-users, such as educational agencies (schools, universities), low income/developing world research and industry or any laboratory without access to clean room facilities, enabling the fabrication of robust, reproducible microfluidic devices.