Dogs chew to relive boredom, fight stress and work off excess energy. They may also chew as a symptom of separation anxiety. Regardless of the reason, chewing on baseboards presents a different problem than chewing on shoes or other household items. You can't put the baseboards away to treat the problem, so you must teach your dog not to chew, and limit his exposure to the baseboards until he understands the rules.
Use a taste deterrent. Taste deterrents, like their name implies, make whatever they are applied to taste bad, making it unappealing to your dog when he starts chewing. Taste deterrents are typically safe to use on most surfaces, but you may want to apply a small amount to a hidden area of your baseboard before spraying it over the entire area.
Keep an eye on your dog. This is the easiest way to prevent your dog from chewing on something you don't want him to chew on. When you are distracted or leave the house, put him in a crate to prevent him from chewing.
Provide physical and mental stimulation. A well-exercised dog is less likely to develop bad habits than one who spends the day alone, without stimulation. Take your dog for frequent walks, play games with him and provide toys that require him to work for a reward.
Treat separation anxiety. If your dog only chews when you are gone, he chews near the exit to the house, and the behavior is accompanied by barking, whining or howling, frantic running through the house, and even urinating in the home, your dog may be suffering from separation anxiety. This is a complex problem that requires thoughtful work with your dog. Consult your veterinarian, who may be willing to provide a prescription medication to help your dog deal with the separation. In the meantime, minimize the amount of time you are away from your dog, and keep him in a crate or other safe area while you are gone.