AbstractFlow electrolysis cells are essential for the scale up of synthetic organic electrochemistry. We have developed a simple and inexpensive parallel plate flow cell that can be easily assembled using a stack of laser‐cut Mylar foils, which act as gaskets, insulating material, interelectrode gap and flow channel. The ease with which the laser‐cutting pattern can be customized has enabled the development of interelectrode separators with mixing geometries, which improve the mass transfer and thus the current efficiency. The performance of the flow electrolysis cell has been evaluated using the anodic decarboxylative methoxylation of diphenylacetic acid as model transformation. Very high conversions and selectivities have been achieved with single‐pass processing, with nearly quantitative current efficiency in some cases.