The invention generally relates to a fuel processor design and a method for manufacture. In one aspect of the invention, a fuel processor assembly has a first plate and a second plate that are mated to form a plurality of reactor housings and channels to direct the reactants. At least one of the first and second plates has an inlet orifice feature adapted to receive a hydrocarbon stream, and at least one of the first and second plates has an outlet orifice feature adapted to exhaust a reformate stream. In some embodiments, a third plate and a fourth plate can be mated to enclose the first and second plates so that a coolant can be circulated between an external surface of the first and second plates and an internal surface of the third and fourth plates.