Both the litter box and Second Nature dog litter can be purchased at PetsMart, PetCo, and most pet stores. I have actually begun using the Petco Dog Litter in place of Second Nature because it is a little cheaper. Both products work exactly the same. Cavalier King Charles Spaniel puppies will occasionally chew on the litter and it is ok if they ingest it, but most of the time they will just chew on it a little bit and then find something else to chew on.
I recommend families that work full time and adopt a 10 week old Cavalier King Charles Spaniel puppy to purchase a large crate that will be large enough to place a bed, litter box, and attach a water bowl to the crate if your Cavalier King Charles Spaniel puppy will be left at home for periods longer than 5-6 hours during the day. Puppies do not fully obtain the capacity to withhold elimination until around 16 weeks of age. By having the larger crate with a litter box to use when you are gone longer than 5 hours helps to keep your Cavalier King Charles Spaniel puppy from experiencing prolonged anxiety in case they do need to eliminate in your absence.
If you have a Cavalier King Charles Spaniel that has not already been previously litter box trained by the breeder all you need to do is add the litter box to their crate and they will automatically begin to use it if they need to. The idea is to keep the crate area confined to only a litter box and a small bed area. Puppies automatically know to leave their bed in order to eliminate and the litter box will become the only other available location. Once your puppy eliminates for the first time in the litter box give lots of praise. If you give your puppy run of the house a litter box will "NOT" work because they are too young to remember to think about a litter box when they need to go. Therefore, if you are not able to give your puppy all your attention then it is always best to keep him in a crate or small designated area with the litter box and then your puppy will be able to remember to go in his litter box when he feels the urge.