I try to avoid repotting trees being layered as the idea is to encourage the most vigorous growth possible, but a gentle repotting (in which not too many roots are removed) could be ok. I also typically start layers in spring - a couple of months after repotting - but I haven't tried a layer with black pine so I don't know how it might work in different seasons.
Another option is to slip the pot off and set the rootball in a larger container with only minimal root-work around the edges of the rootball.
I don't know of many black pine air layers that have worked. Is there no way to check for roots by digging through the soil?