Sprinkle 1 teaspoon salt, garlic powder, and 1/4 teaspoon black pepper over chicken legs and thighs.
Heat 1 tablespoon olive oil in a Dutch oven over medium-high heat. Place chicken legs in the Dutch oven, skin-side-down. Sear until golden brown on both sides, about 10 minutes total. Transfer legs to a plate. Discard used oil.
Pour 1 tablespoon olive oil into the hot Dutch oven. Add thighs, skin-side-down. Sear until golden brown on both sides, about 10 minutes total. Transfer thighs to a plate. Discard used oil.
Reduce heat to medium-low and add remaining 1 tablespoon olive oil to the hot Dutch oven. Add bacon; cook until crispy, about 8 minutes. Drain bacon over paper towels on a plate.
Increase heat to medium and add onion, green bell pepper, celery, and a pinch of salt to the hot Dutch oven. Cook until onion has released its moisture, about 5 minutes. Add minced garlic, paprika, and red pepper flakes. Cook, stirring often, to combine flavors, about 4 minutes more.
Return chicken legs and thighs to the Dutch oven. Pour in chicken stock to only partially cover chicken so that skin remains crispy. Scrape up the bottom of the pot. Bring to a boil, cover, and reduce heat. Simmer until chicken is no longer pink at the bone and juices run clear, about 25 minutes. An instant-read thermometer inserted near the bone should read 165 degrees F (74 degrees C). Remove from heat and transfer chicken to a plate.
Whisk sour cream and flour together in a bowl. Add 1 cup of hot chicken stock from the Dutch oven to the sour cream mixture to temper it. Whisk the mixture into the Dutch oven quickly so that the sauce does not clump. Add 1 teaspoon salt and 1/4 teaspoon black pepper.
Return Dutch oven to medium-high heat and bring to a boil. Boil gently, uncovered, until sauce is thickened slightly, about 5 minutes. Return chicken parts and bacon to the Dutch oven; stir gently to combine.