You can build the playpen square or rectangle or hexagon......whatever fits. They now apparently come with a top? I didn't use that but I did go from the plastic short one to the tall metal one because she could climb it. Crate inside with door open and comfy bedding. Good quality toys because cheap ones break apart and doggies can choke. Kong is great filled with peanut butter and frozen. Pee Pad or newspaper on one end, he will definitely use it. Water bowl and food dish on the other. Hope he isn't aggressive enough to rip up your floor......only seen this once with a boxer.
Eventually you can just use the crate when he's around one or so. Peeing outside will still be first choice when you can and it will all come together. Done this with many dogs.