Last time we glued together your butcher block. When it’s dry, cut the finished block to length, and sand any uneven places on the surface. If you can get access to a surface planer, you’ll save a lot of time and elbow grease.
You’re going to finish the top and sides with a food-safe oil, but you may want to protect the bottom of the block as well. You can use any normal finish here, from linseed oil to urethane. Before finishing the top, attach the block to your island or cabinetry by screwing from below.
Now, some real butchers don’t finish their blocks; scrape down the surface every day, exposing a whole new layer of fresh material. But you don’t need to go that far.
An oil finish — often mineral oil — will help protect the wood from water and stains, and help keep food odors and bacteria from getting into the wood. It’s also easier to maintain and repair damage when you have an oil finish as opposed to urethane or varnish. Warm up the oil a bit, and apply a thick coating over the surface, using a soft cloth along the grain. Let this soak for a few hours, and then rub off the excess. Repeat this at least twice.
Then start using it.
To maintain your butcher block, apply a single coat of oil every couple months, and sand the surface every year or two. Don’t let water sit on the surface; wipe it up fast. For cleanup, use a damp cloth with detergent, and rinse with a clean, wet cloth. After cutting meat or poultry, wash the surface, then rinse with a solution of vinegar and water, or rub salt in with lemon.