Make the broth first ahead of time. Combine all the ingredients in a large pot and bring to a boil then simmer for 45 minutes. Let it cool then strain. You can discard the vegetables. Save the rest for something else.
Melt butter in a medium saucepan over medium heat. Add the onion and saute for about 5 minutes until soft. Season with salt then add the flour. Cook for 1 minute. Stir in the broth and cook for 5 minutes until thickened. You can add more broth if it's too thick. Add the herbs and lower the heat and simmer for few more minutes. Season with salt and pepper according to taste. Ready!
Recipe by Gluten-Free by Jan at https://glutenfreebyjan.com/gluten-free-homemade-gravy/