Don't worry about the slip. Maybe he isn't a fancy Christmas dinner, but he isn't lacking in value (until he is allowed to chase hens LOL).
It's a matter of cooking. I would probably cut up a slip and use him in a soup with potatoes, onions, spices, and whatever other vegetables you want. There are plenty of appropriate dinners coming up now that the holiday season is over.
If you can get raw milk, it's great for tenderizing _slightly_ tough meat, along with a bit of meat tenderizer. Otherwise, try buttermilk. He's still young, so the meat should be good, slow-cooked.
I've had meal success with intact Roo rested overnight in raw milk with a bit of meat tenderizer and then slow-cooked for 3.5 to 4 hours. Slip should be better.