Heat 1 tablespoon oil in a large pot or Dutch oven over medium-high heat. Season 1 ½ pounds chicken thighs with kosher salt.
Once oil is shimmering, add thighs, skin side down in pot, and cook, without moving, until skin is deeply golden brown and crispy, about 10 minutes. Flip and cook 2 more minutes; transfer thicken to a plate.
Reduce heat to medium and stir in 1 cup rinsed rice, cook 2 minutes. Add 1 cup carrots, 1 cup celery, 1 cup onion and 3 chopped cloves garlic; season with 1 teaspoon salt and cook until starting to soften, about 5 minutes. Meanwhile, remove and discard chicken skin.
Add 8 cups broth and browned chicken (and any accumulated juices) to pot, bring to a simmer and cook until chicken is cooked through, about 8 minutes. Transfer chicken to a bowl and remove pot from heat.
Once chicken is cool enough to handle, remove meat from bones and shred meat into small pieces using two forks; discard bones.
Add shredded chicken, 2 cups peas, ⅓ cup dill and 2 tablespoons lemon juice to pot; season with salt and pepper to taste.