That's one method. Another is to build a frame that fits around your cutting board. It has to be wide enough so that when the cutting board is centered in the frame, your router bit will cut the groove at the right distance from the edge of the board. To keep the cutting board centered you will cut spacer blocks to fit between the cutting board and the frame. This is a good method for grooving many cutting boards.
Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.