Preheat oven to 325 and line a large baking sheet with parchment paper.
Place the sliced in a bowl with cool water to help clean for 5 minutes. (Leeks hold a lot of dirt in between the layers and this helps to get it out). Rinse well.
Using a paper towel, pat the chicken dry.
Add leeks and lemon to the sheet pan. Lay the chicken on top, skin side up. Drizzle the chicken with olive oil and rub until coated well. Sprinkle evenly with salt, pepper and smoked paprika.
Roast for 75-90 minutes, until the chicken is cook through or internal temperature reaches 165 degrees Fahrenheit. This will depend on the size of your chicken breast. Mine took all of the 90 minutes. When the cook time is done, turn oven to broil and cook until the skin crisps up a bit, about 2-3 minutes, watching carefully and being careful not to burn.