Trim the chicken thighs of visible fat. Season on both sides with salt, pepper, and 2 Tbs of the minced oregano.
Heat 2 Tbs of olive oil over medium high heat in a large dutch oven.
Sear the chicken on both sides until the chicken browns. Do this in batches if your pot isn’t big enough to hold all of them without crowding. Add any juices from the chicken back into the pot when you add the stock in Step 7.
Remove chicken from pot, turn the heat down to medium and heat the remaining olive oil
Add the leek and garlic and sauté until the leek softens and is lightly browned.
Add the wine, and stir -scraping up the browned bits from the chicken.
Add the stock, sweet potatoes, bay leaf, and spices and stir to combine.
Add the chicken back to the pot and nestle them just below the liquid surface.
Bring to a simmer, cover, and cook until the chicken is done and the sweet potatoes are tender (but not mushy), about 30 mins.
Smash a few of the sweet potatoes against the side of the pot and blend into the stew.
Remove about ½ cup of the liquid and blend it with the flour – adding back in to thicken the liquid.
Leeks: Slice the leeks finely, and then add to a colander. Rinse, under running water. Then rinse again. Strain, and they're ready to use.