When adding spices I always add Post ferment. You can easily over do spices and you won't have a gauge of how it will taste until it has femented out ie you know what the base flavour is.
I would sanitise the spices in a little boiling water then add to a muslin bag or hop sock weighted with a spoon and put it in the fermented beer. then every day take a sample to see how it is getting on. Once you have the desired tasted take it out. But as I said aire on the side of caution, its better to have a hint of flavour than a full on in your face shouting from the rooftops flavour which completely destroys your beer.
I made that mistake once with a spiced IPA, you only make it once. :lol: :lol: