If you really want to create all of the tortuous paths, plates or whatever in the CAD feel free. Then mesh with good resolution. Otherwise, use the porous media, and define the cell zone in geometry for use in the solver.
Flow in as a liquid is fine, remaining boundaries may be open to ambient? Stopping the liquid just pouring out the other end may be the difficult part. Why would the liquid not leave the porous zone if there's enough of it? Remember fluids will always look for the path of least resistance.