The last remaining publication from Emilia’s PhD studies just appeared in Electroanalysis. Immobilization of enzymes can significantly prolong the stability of an assay, but on the other hand depending on the method chosen, it can also influence the porous structure of the paper and provide additional charge. Having this in mind we first evaluated how 4 distinct methods of immobilization impacted the flow in a paper-based channel. As it is well known that changes in the architecture of paper-based devices are also crucial for its performance, in the next step, different shapes of the enzymatic zone were tested, including electrochemical measurements, as well as simple COMSOL calculations. Our goal was to achieve optimum time of the enzymatic reaction, separation of peaks and the time of measurement. Best results were obtained for a constantly narrowing channel. A proof-of-concept analysis of mixed samples of uric acid and glucose was performed. The manuscript also contains a few valuable guidelines regarding the reproducibility of enzymatic paper-based devices with electrochemical detection.