Disclosed herein is a magnetic field generator and method for assembling the same for a magnetic resonance imaging system, the method comprising: establishing a layout for a permanent magnet of a magnet assembly comprising a pole piece, a ferromagnetic plate yoke and a permanent magnet. The method also includes populating the layout with a plurality of mock-up sticks and block retainers to form a mock layout for the permanent magnet; and installing a magnet block in place of at least one mock-up stick of the plurality of mock-up sticks. Installing the magnet blocks includes pushing the magnet block along a selected slot formed by the displacement of at least one mock-up stick of the plurality of mock-up sticks.