Another good thing about them being in a bow or on a diagional, is when cutting square objects eventually & probably sooner than you may think, your cut will center one of the slats & burn the entire top edge from that particular slat.
I built my table to place the slats in a bow. The way I have them arranged the slats require NO fastening other than the tension of the bow against the slat holders. This makes them very easy to replace once the top surface is hacked up so bad that sheets will no longer lay flat & level.
If it works.....Don't fix it!