My FCOM PRO-NOR-SOP "Takeoff" section says "at acceleration altitude, set thrust levers into the climb decent then select pack 1 on and then select pack 2 on (if applicable)" which says to me judgement may be used - I.e. should you be doing a flight test, complying with a MEL O procedure or a depress ferry you may configure as desired.
Depending on your MSN number, the later model Bleed Management Computers (BMC) will automatically close the affected bleed if the engine is shut down so pack selection in that case would be irrelevant unless the cross-bleed was set to open for some reason - MEL?
With the cross-bleed switch in 'auto', IIRC the cross-bleed will be closed and the affected pack inlet valve will close automatically or in this case remain closed.
In all models it is my understanding that the BMC will close the affected engine bleed if there is reverse flow through the bleed valve (I.e. of a failed engine), so again in this case (failed side) pack selection would be irrelevant.
Following the failure, if a pack was necessary, it would be logical to me to switch on on a pack on the serviceable side and change bleed switches only as directed by the ECAM or QRH.