The controlled assembly of nanomaterials is essential for constructing functional materials used in solid-state applications such as electrochemical sensors and optoelectronic devices. While extensive studies have focused on solution-based assembly, assembly at solid-liquid interfaces remains challenging due to the difficulty in controlling structure and orientation. In this work, we present an innovative liquid–liquid phase separation (LLPS) approach for assembling and immobilising nanocarbon materials1 onto electrode and 2D material surfaces. During LLPS, a homogeneous solution spontaneously separates into two immiscible liquid phases, driving the self-organisation of nanocarbon architectures with defined alignment and packing. Confocal microscopy and quantitative analysis reveal that the intermediate LLPS pathway critically determines the resulting nanomaterial configuration. Furthermore, mesoporous and granular structures generated through the Ouzo effect during LLPS contribute to enhanced surface area and tunable porosity. The resulting architectures exhibit distinctive optical and electrochemical properties, enabling efficient adsorption and highly sensitive detection of environmental contaminants2-3. This LLPS-driven assembly offers a simple, controllable, and scalable route to engineer nanomaterial structures directly on solid surfaces, opening new opportunities for the design of adaptable, high-performance materials across diverse applications in sensing, catalysis, and energy conversion.