Thin single organic crystals (≤1 μm) with large area (≥100 × 100 μm²) are desirable to explore photoinduced processes using ultrafast spectroscopy and electron-diffraction. Here, we present a general method based on spatial confinement to grow such crystals using the prototypical proton transfer system, 1,5-dihydroxyanthraquinone, as an example, and provide the protocol for optically characterizing structural dynamics to enable proper assignments using diffraction methods.