For such high currents there are basically two options:
1. Distribute the supply over several stages connected in parallel. Like what is done for CPU supplies on motherboards. Doable because the voltage is quite low, and the load is mounted on the same PCB, surrounded by the supply circuitry.
2. Move the power components off the PCB, use modules which mount directly to the chassis or a heat spreader. The PCB will only contain low power control, sensing, and gate drive circuitry.