Slow cooker creamy chicken and wild rice soup

Ingredients

• 4 cups chicken broth
• 2 cups water
• 2 boneless, skinless chicken breasts
• 1 package of Rice-a-Roni long grain and wild rice
• 1/2 teaspoon salt (plus more to taste)
• 1/2 teaspoon pepper
• 3/4 cup all purpose flour
• 1/2 cup butter
• 2 cups half and half
• 1 cup grated carrots
• 1 cup diced celery