I do them once a week for my gang..they love em. You have to be careful not to introduce them in large amounts..unless you love to clean up runny poops..my small dogs get a total of about a 1"-2" square daily and my big dog get about 5" square.
I buy the big sweet potatos (yams) in some places and cut them in 1/8" strips. You can either use a deyhdrator or put them on a cookie sheet ( I use a pizza pan with the tiny holes all over) and bake them at 200 for several hours. I actually like using the oven better than the dehydrator, the dogs seem to like the bit of crisp to the edges. I leave them to bake for anyware from 6-8 hours and flip them over every hour or so.
One large yam lasts my 4 small and 1 large dogs 1 week and fills the large roung pizza pan.