As soon as the beer is at FG
Keg it in your usual manner and carbonate it.
~35F Beer 36 hours at 30 psi and then to serving pressure till it's at the level you want. This will take a total of 2-5 days I would guess.
Once it's carbonated to your liking, unhook and place somewhere warmer (cellaring temps ideally) to condition.
Now you can sample it over time as it ages. This is what I would do for a big beer that required some time to mellow. The beer is safely stored in a SS CO2 pressurized light impenetrable container ideal for long term storage/aging wherever you want.
Even ales can cold condition so it is not absolutely required to place the keg outside of your fridge. A good option if space is limited.
The source of the CO2 in the beer doesn't matter a damn to the aging process.