The synthesis of diamond crystal from powder mixture of graphite and catalyst alloy is a well known process but it is limited to relatively small crystal dimensions due to the size of the conventional compression chambers. In this work the design and construction of a novel high pressure multi-anvil device with a parallelepiped shaped compression chamber is presented. The design allows the length of the chamber to be limited only by the working space of the press equipment. A four horizontal anvils device was constructed for a specific 2500 ton press with a 600mm working space. The efficiency of this construction was tested in diamond crystal synthesis.