Flange is placed. Good deal.
Rocking is usually because the base is not completely flat, rather than the toilet being high-centered by the closet flange.. You want shims. With no wax, place shims. Keep the shims in place. Lift the toilet. Drop the wax, and drop the toilet on wax and shims.
There are different favorites for shims. Terry prefers to put the shims aft. I think that makes them less visible, plus it tends to leave a tad more water in the bowl.
At what point you trim the shims to length will be personal choice. My method was to mark the shim, take it to a saw to cut to length, and then to put the shim into place with the trimmed edge pretty much at the toilet edge.