What is the best method for placing text on copper?
If this question is asked on the aesthetic look of the text then there really is no better way than the look you want to achieve. It comes down to your opinion.
There are some additional things to consider when making that aesthetic choice.

You could move the text to be in actual copper but have the cutout around it moved over by the edge of the board / plane. When I do this I try to carefully align the outer edge of the text so that it is right in line with where the edge of the plane copper would have been. Here is an example of how that can look.



You could consider making the text itself be a negative object that cuts holes in the copper layer. Implementing this may very well be CAD package specific. Here is an example of this.