Power and ground lines in a PCB
The bottom of the PCB should be a solid ground plane. On the Top Layer you can use either the complete plane as +24V, or use Polygons to make a 24V Layer. You can use a trace width calculator like this to find the required dimensions for current and voltage. Make sure you route away the high voltage from other components like mikrocontroller or logic elements.
P.S. The Circuit will destroy the mosfet. The gate of the IRFZ48 only works up to 20V, not 24V. You either have to select another mosfet, or use a zener diode to lower the voltage.