Preheat the oven to 220° C (430° F).
When the oven is hot, place the bones in a tray and roast for 25 minutes.
25 minutes later, take the tray out of the oven and spread the tomato paste on the bones.
Add the vegetables on top of the bones and roast for another 20 - 25 minutes.
Place the roasted bones and the vegetables in a large pan and add enough cold water to cover the bones and vegetables, thyme, bay leaves, parsley stalks, and peppercorns.
Simmer on very low heat for 6 to 7 hours, skimming the scum on the surface from time to time. Don't let it boil or don't stir it during cooking.
At the end of the cooking time, remove all the solids and discard them.
Pour the stock through a fine sieve into a clean pot and let it cool down.
Pour the stock into the weck jars or containers to store in the fridge for up to a week or in the freezer for up to 3 months.