In a dutch oven or enamel baking dish, add oil and warm through on medium heat until it shimmers.
Season thighs with all season's salt, chili flakes, and brown on all sides and remove and set aside. (it will not be cooked through, don't worry - it will get cooked later on.)
Turn heat to medium and saute leeks and garlic together. Add a touch more oil if needed.
Once they are translucent and soft, add smoked paprika, lentils, tomatoes, and white wine. stir together.
Stir in broth/stock and allow lentils to cook for about 5-10 minutes.
While you are cooking the lentils, Preheat oven to 375 F
Add in squash and chicken back to the pan. Add in a touch more broth if it looks like it needs a bit more moisture.
Place in the oven (uncovered) and pull out when lentils are cooked through. ( ~ 40-60 minutes). Serve hot and add a dash of hot sauce, salt, or pepper as needed.