To begin, it is recommended to perform an aggressive sanding with an 80-grit sandpaper to remove knife marks and stubborn stains. Then, continue with a sanding at 120 grit to smooth the surface of the board. It is important to choose a high-quality finishing oil, which will be more resistant over time and facilitate maintenance. Avoid mineral oils, as they do not provide resistance and require frequent application (every week). For more information, here is a detailed blog post on finishing and restoring cutting boards and butcher blocks.