Sorry...yes put the diode across the coil as in the diagram.
When the relay contacts open the solenoid connection to the relay goes several hundred volts positive forward biasing the diode allowing the current to harmlessly re-circulate around the diode/coil parallel circuit.
When the relay contacts open the solenoid connection to the relay goes several hundred volts positive forward biasing the diode allowing the current to harmlessly re-circulate around the diode/coil parallel circuit.