Bone Broth

approx 2-3 lbs bones
Some use just beef bones (esp marrow bones), some insist on using the bones of different animals, at least 2 (beef, lamb, poultry)
place in large stock pot, fill with cold water plus:
2 T apple cider vinegar
Let sit for 20 minutes in cold water before heating.
any vegetables desired - celery, radishes, broccoli, etc. If you are making this soup "keto" best not to use root vegetable which are starchy and carby
Vegetables won't be edible after cooking so long, so I use this soup to get rid of stuff that's almost ready to trash anyway
fresh ginger slices
dill, fresh or dried
sea salt
spices to taste

bring to boil. simmer 8-48 hours.  (Again, this is a machloket. 8 hours is fine.)
add water as needed.
Strain soup through strainer or colander.