Shop this look.
This mockup includes two of my square prints with a black frame.
To achieve a similar look, get two prints in your prefered size and look for a frame that is at least 10"/ 12" larger than the print (that has a white mat with an opening just a tad smaller than your print to ensure that the print is snug.)
For example: a 20" print would fit inside a 30"/32" frame with a 19.5 mat opening. There would be roughly 5" white space around the print, similar to what is showing.
If you can't find a white mat board in your desired opening size, I suggest purchasing the frame in your desired size, then going into a local frame shop to have a custom mat board cut to your specifications. Cutting a mat board is inexpensive.