Beef Stock - Untested

https://www.reddit.com/r/Cooking/comments/1oi9qn/beef_fat_trimmings_suggestions_on_what_to_do_with/ccs7kfw/

https://kalynskitchen.com/how-to-make-beef-stock/

https://goodcheapeats.com/how-to-make-beef-stock/

https://cooking.stackexchange.com/questions/20390/why-skim-scum-from-the-surface-of-a-simmering-stock#:~:text=The%20scum%20is%20denatured%20protein,leaving%20it%20grayish%20and%20cloudy.

3-4 lbs beef trimmings, cut into small chunks
1 onion thickly sliced
1/2 cup red wine
10 cup water
2 carrots
1 rib celery
2 clove garlic
2 bay leaf
5 peppercorns
3 whole cloves
sprig fresh rosemary
sprig fresh thyme
1 tsp salt. 

1. Roast the scraps in a 400F oven until nice and brown. This could take up to an hour.
2. Bring the water and wine to a gentle boil and add the roasted scraps, the onion, carrots, celery, garlic, herbs and salt.
3. Bring back to a boil, the turn down and simmer for 3-4 hours. If you want to broth to be clear, remove any foam that develops on the surface. This foam is just denatured protein a bit like egg white. If you don't remove it, it will eventually break back down into the liquid and will make it cloudy. 
4. Allow to cool, then refrigerate to remove the layer of fat floating on top (which can be used for cooking).
5. Strain to remove the scraps, vegetables and herbs, then return the liquor to a simmer and reduce as you see fit (could I do this in a slow cooker?)