The epoxy won’t affect the functionality of the electronics, because it’s not conductive. But, you need to make sure the device wiring is completely finished, and you need a way to provide power. For power, you could use a battery, but you won’t have anyway to charge or replace it when it dies. A better option is to do what Kodera2t did and embed a wireless charging coil into the epoxy with the rest of the device — an ESP32 in this case. Once you pour the epoxy, you’ll be left with a functional device that doubles as decoration.