This is a picture frame using a Celtic braid design.  It can be 3D printed or cut out of wood using CNC.  

If 3D printing with a smooth print bed, it can be printed such that the front face is flat on the printer bed without any support or raft.  If your print bed is rough or has marks, then print the frame such that the front face is upward.  You will then need support for the overhang.  

For CNC I used a 1/4" end mill followed by a 1/8" end mill for the finer outline.  To cut the final Celtic pattern I used an engraving end mill.  This cuts well on hardwood  -- I used sapele with a varnish and it came out very nicely.

You will also want to source a couple of small wood screws, and a thin plate of glass to give it the final polish.