What can I do to make sure my puppy doesn't develop seperation anxiety?

My 11 year old dog I adopted when she was 7 had severe seperation anxiety. Loved her but it caused nothing but serious inconvienence for myself and my family and we couldn't cure her of it no matter what we tried. Last week we got an 12 week old puppy. He's clingy and doesn't ever want to be left alone, as expected for his age. What should I be doing to make sure he doesn't get seperation anxiety as an adult? I want to be able to let him be alone at most 4 - 5 hours in a day outside of his cage.