Heat olive oil in a large pot over medium heat.
Add the chicken thighs, seasoning with salt and pepper, and brown on all sides.
Remove the chicken and set aside while you sauté the onions and garlic in the same pot.
Add carrots, celery, and potatoes to the pot, stirring occasionally until they begin to soften.
Return the chicken to the pot and add the chicken broth, thyme, and rosemary.
Bring the stew to a boil, then reduce to a simmer and cover.
Simmer for about 30 minutes, checking for tenderness on the chicken.
Add green beans and continue to simmer for an additional 10 minutes.
Adjust seasoning with salt, pepper, and lemon juice before serving.
Serve hot with crusty bread or over rice, if desired.