Wow. I've gone what I thought was hardcore on carnivore. Beef is king, and I would ask for scrap fat every time I'm at the butcher or grocer. Would render down fat, and save the "cracklin" for burger toppings.

One of my favorites, even if it sounds gross, is to sous vide ground beef at around 138f for several hours. This saves all juices. I then put the entire brick with juices in the Vitamix, plus salt and some bbq sauce. Not to blend it, but to break it out of its block form. Turn it into a bowl of whole use beef.

Another favorite of mine to get fat in, is homeground burgers. Get a (fatty) roast on sale, and then lots of scrap Fat. Boil all for one minute to kill surface bacteria. Then make medium rare burgers. By cooking to 135 rather than 165, can retain lots more fat and juices.

Doesn't get anywhere near 88% fat.... But I'm sure I hit 40% with some of these techniques.