Put oven rack on lowest position. Heat oven to 350.
Toast 3/4 cup Flour in Dutch Oven over medium heat until just beginning to brown whisking constantly (about 5 minutes). Then take off heat and whisk in oil till smooth.
Cover and place in oven for 45 minutes or so, till deep brown and fragrant.
Transfer to stovetop and whisk to combine. Add Onion, Bell Pepper and Celery and cook over medium heat stirring often, till softened. (about 10 minutes)
Stir in remaining Tbsp of Flour, Garlic,Thyme, and Cayenne pepper. Cook about a minute. Add Tomatoes and cook another minute, until dry.
Slowly whisk in Chicken Broth and fish sauce. Season Chicken and add it in and bring to a boil.
Reduce to medium heat and simmer, covered, until tender (about 30 minutes) Transfer chicken to plate to let cool, then cut into bite size pieces, and put meat back in (throw away bones)
Stir in sausage and okra, cook about 5 minutes, then add shrimp and cook 5 more minutes.