Lay the bones out on a roasting pan in a single layer and season with sea salt and pepper.
Bake bones for 30 minutes and then remove from the oven.
Meanwhile chop the carrots, celery, and onion into equal sizes.
Turn the bones over and then smear the tomato paste on them. Layer the veggies with the bones. Bake for another 30 minutes.
Once baked, add the bones and juices to the crock pot and reserve the veggies in a sealed container in the fridge. They’ll come in to play later.
Add all the other ingredients to the crock pot and fill with water, making sure to leave just enough room for the reserved veggies you will be adding later.
Cook on low for 24-36 hours. During this time, go on with your daily life while basking in the gorgeous aroma. Add the veggies in about 6-8 hours before the end of your cook cycle.
Once the wait is up, strain the broth with a fine metal strainer.
Chill the broth in the fridge overnight. Skim off the chilled fat which forms on the top.
Store in the fridge for up to 3 days OR do what I do: Freeze the broth in an ice cube tray and then save the cubes in a freezer bag. Every morning I heat one cube with an equal amount of water, add seasoning, and drink with my breakfast. This is a concentrated bone marrow broth, so I like to use a 1:1 ratio of broth to water. If you have a bigger Crock Pot then it won’t be as concentrated.