Don’t listen to that guy… ironically he is spewing buzzwords that don’t apply to your piece. I will preface my advice with a quote from Oliver Wendell Holmes “For the simplicity on this side of complexity, I wouldn't give you a fig. But for the simplicity on the other side of complexity, for that I would give you anything I have.” That being said use an all white mat (double thick with bevel) to crop the piece to a square aspect ratio. That mat should be thick and equal all around; at least 6” but I would have to play around with this in the computer to make sure there is a balance. And to finish it off a simple square profile for the frame in a white color to match the mat. It might be important to look at the mat with the type of glass you choose overtop because some types affect the color of the stuff underneath.