Here you go ...

http://walking.about.com/cs/diet/a/recipecarnitas.htm

Beef does not do as well in a crock pot but fatty pork does.

I rub the fresh ground cumen mixed with oil over the roast 1st, the whole process took 10 hours in my pot. You can check with a meat thermometer if in doubt. I just slice the meat thick after it cools then fry up in butter as needed. The cilantro is optional. True carnitas are seasoned then deep fried in lard they are yummy and very filling.