With a flat slide valve concept, when compared to conventional piston spool valves, reduced leakage and increased service life could be achieved. In order to achieve a reduction of leakage flows and guarantee the adjustability of the valves at the same time, a correct design of the pressure compensation is essential. The magnitude of force depends on both the operating point of the valve and the position of the slider. Due to the design of the flat slide valve, it is possible to use ceramic semi-finished products for the main stage, which consist of control plates and a slide plate. The geometries are simple enough to be inexpensively manufactured with sufficient accuracy, using a ceramic pre-product using laser cutting technology. This article introduces the concept of the flat slide valve for a proportional 4/3-way valve. The design of the valve, including the design of the metallic main stage is presented. This includes the design of the flow channels, which have to be suitable for ceramic materials. Furthermore the design of the actuator and hydraulic circuit for testing is presented. With the shown design, the function of a 4/3-way valve, known from piston spool valves, can be implemented with a linear behavior between slide plate deflection and opening flow cross section.