Peel and cut the onion into eighths. Coarsely chop the celery and carrots. Briefly press the garlic with the skin on with a knife. Put all the ingredients in the crockpot. I cook salt-free, others season with 1 teaspoon of salt. Cook in the crockpot over low heat for 8 to 10 hours. Then strain the contents through a sieve.
The broth is easy to freeze in portions and can be used for soups and sauces.