1. Assess the overall condition of the cutting board: you may need to make peace with the end of your warped boards, butcher blocks made from multiple wood strips that are coming apart, and ones that look like they’ve been used for chopping wood. Cutting boards that have minor scrapes and dents, are simply dried out on the ends, or just seem a little gross can be resuscitated.
2. Identify any problem areas: do the ends need some love? Is it simply that the surface looks like a cat has used it as a scratching post? or is it just a little dry? Here we will assume all of the above, but localizing the problem and addressing it specifically using one or a combination of the approaches below is fine.
3a. End issues: if the ends of the board are gross, the wooden strips are just starting to come apart, or even if the board is just the wrong size for your kitchen, it makes sense to remove a bit of material with a table saw. Always use proper personal protective equipment when using a saw. Set the height of a finishing blade just higher than the thickness of the board and remove some material from each end. This might mean 1/4″ for clean-up or refinishing, or more if the slats are coming apart.
3b. Scratches: here, the surface of the board needs to be refinished. The two main ways to do this are with a planer and with a sander. If you happen to have a planer around that can accommodate the board, plane the board until most of the scratches are gone. If you don’t, or if the scratches are mostly superficial, use either a handheld electric sander or a sanding block, working through rough grit (60-100) to finer (200), until the surface is like glass.
3c. Dry wood: this will be the final step, regardless of other treatments for your masterpiece. When wood dries out, it shrinks, which can mean delamination of a strip cutting board as well as opening up micro-fissures in the surface that can trap bacteria and other grim during use. To prevent this, use a food-grade oil, such as butcher block oil. Some use cooking oils, but beware that these may go rancid over time (really, you’ve put so much work in, just splurge and get the real thing). Using a cloth, pour a small amount of oil onto the wood and work it in by rubbing. Note that dry wood and newly finished surfaces may take a few coats over the day or week.
4. Maintenance: keeping your board in tip-top shape requires only a few minutes a month. When you have a few minutes, wash your board with a mild soap and rinse well with water. This will remove any bacteria or small food waste that may have been wedged into the wood by especially enthusiastic knife work. Dry the board thoroughly with a clean dish towel. Now re-oil the board as in 3c, wiping any excess and leaving it in a dry place for the oil to soak.