Pat the chicken dry with paper towels and season with salt and pepper. Heat the oil in a 12-inch skillet over medium-high heat until just smoking. Brown half of the chicken on both sides, 5 to 8 minutes per side, reducing the heat if the pan begins to scorch. Transfer the chicken to a plate, leaving the fat in the pan. When cool enough to handle, remove the browned skin from the thighs and discard. Transfer the chicken to the slow cooker. Return the pan with the fat to medium-high heat and repeat with the remaining half of the chicken.
Pour off all but 1 tablespoon fat from the pan. (Add additional oil to equal 1 tablespoon if needed.) Add the onions, paprika, cardamom, and 1/4 teaspoon salt and cook until the onions are softened, 5 to 7 minutes. Stir in the garlic and cook until fragrant, about 30 seconds. Stir in 2 1/2 cups of the broth, the apricots, and cinnamon stick, scraping up any browned bits, and bring to a simmer. Pour into the slow cooker.
Cover and cook on low for 3 hours. Quickly stir in the chickpeas, replace the cover, and continue to cook until the chicken is tender, about 1 hour longer.
Transfer the chicken to a large serving dish and tent loosely with foil. Discard the cinnamon stick. Set the slow cooker to high. Whisk the remaining 1/2 cup broth and flour together until smooth, then stir into the slow cooker. Cover and continue to cook until the sauce is thickened and no longer tastes of flour, 15 to 30 minutes longer.
Stir in the cilantro and lemon juice and season with salt and pepper to taste. Spoon the vegetables and some of the sauce over the chicken and serve with lemon wedges, passing the remaining sauce separately.