You should fully oil every part of the cutting board. Oil should be applied to both sides of the cutting board, as well as the edges. Allow the board to soak the oil in for 10-15 minutes, leaving it propped up on an edge vertically, then wipe excess off. Then allow the board to sit overnight before using.  Oil the board monthly if possible or more if the board is heavily used. This will ensure your Acacia cutting board does not dry out and crack.