Heat 1 tablespoon of the oil in a large Dutch oven over medium-high heat. Add the chicken in an even layer, season lightly with salt and pepper, and cook for 4 to 5 minutes, stirring now and then, until lightly golden and just cooked through. Move to a plate.
Add the sausage to the same pot and cook for 2 to 3 minutes, until lightly browned. Add it to the plate with the chicken.
If using okra, add a little more oil if needed and sauté the okra for 3 to 4 minutes until lightly golden. Set aside in a small bowl; this keeps it from turning slimy.
Add the remaining 2 tablespoons of oil, then the onion, bell peppers, celery and jalapeño. Cook for 5 to 6 minutes until soft. Add the garlic and cook for 30 seconds.
Add the rice, Cajun seasoning, thyme and bay leaf. Stir constantly for about 1 minute, until the rice is lightly toasted and fragrant.
Stir in the crushed tomatoes and 3 cups of stock. Bring to a gentle simmer, turn the heat to medium-low, cover and cook for 18 to 20 minutes, until the rice is tender and most of the liquid is absorbed. If the rice still needs longer, add up to 1/2 cup more stock, stirring as little as possible.
Stir in the okra, shrimp, chicken and sausage. Turn off the heat, cover and let it steam for 4 to 5 minutes, until the shrimp are pink and opaque.
Remove the bay leaf. Stir in the lemon juice, then taste and adjust with salt, pepper or more Cajun seasoning.
Serve straight away, topped with green onions, parsley and hot sauce if you like.