Cook the rice according to the package directions and keep warm.
Make the roux: heat the 1/4 cup canola oil in a heavy pot over high heat until it shimmers. Whisk in the flour and stir constantly for 4 to 6 minutes, until the roux turns the color of milk chocolate. Watch it closely so it does not burn.
Immediately add the onion, bell pepper and celery and stir for 4 to 5 minutes, until softened. Add the garlic and 2 tsp Cajun seasoning and cook 1 minute more.
Slowly whisk in the chicken stock, Worcestershire and hot sauce. Simmer 15 to 20 minutes, stirring often, until it thickens into a sauce. Season with salt and pepper.
Meanwhile, sauté the carrots and okra in the olive oil over medium-high heat for 6 to 8 minutes, until tender and lightly browned. Season with a pinch of salt.
Toss the salmon cubes with 2 Tbsp Cajun seasoning. Heat 1 Tbsp canola oil in a skillet over medium-high heat and sear the salmon about 2 minutes per side, until just cooked through.
Build each bowl: rice, a generous ladle of the gumbo sauce, the Cajun salmon, okra and carrots. Top with the sliced Fresno chili.