How to finish a cutting board!
First you want to sand old wood or new raw wood down to a smooth surface starting at 80 grit and working your way to 220 grit. Once sanded and cleaned finish your board with a non curing finish like platinum finishing oil.
Curing oils can be used but you should not build a finish as when you cut onto the wood your cutting away at the finish as well. Platinum finishing oil is an organic food safe/skin safe wood oil designed for food contact.