Place on top of dressing. Cover with foil. Bake in 400-degree oven for 45 minutes. Remove from broth and dice, pulling meat from neck bone. Add more water, if needed, to make 4 cups broth.
Return giblets to broth.
Blend flour with 1 cup water until smooth. Add to broth. Stir in salt, pepper, and onion flakes. Grate boiled eggs into broth. Cook 15 minutes longer.