Season the oxtail generously with cajun seasoning. Brown oxtail in batches over medium-high heat n a large Dutch.
Remove and set aside.
Add the onions, celery and bell pepper and cook until beginning to soften.
Stir in about ¼ cup instant roux just until combined.
Add the garlic and thyme leaves and sauté for another minute.
Add the red wine and allow to reduce for about 3 minutes.
Add tomato paste and saute for about 2 minutes.
Add the oxtail and pour in the stock, just enough to cover the oxtail.
Reserve the remaining stock for later. Season with cajun seasoning.
Bring up to a boil, cover and then place in a 350 degree oven for 3 hours.
Check oxtail every 45 minutes for moisture. If the stock has evaporated too much, add more as needed.
Remove the lid for the last 30 minutes of cooking to allow the sauce to reduce.
Remove oxtail from oven, then with a slotted spoon, remove oxtail from the pan into a deep serving dish, cover loosely with foil and set aside.
Place cooking liquid in Dutch oven over medium-high heat and stir in intant roux and cook until desired consistency is reached, adding instant roux until that point is reached.
Gently stir in oxtail to coat with sauce and serve with sauce over hot cooked rice.