Place chicken thighs in a resealable plastic bag; cover with pickle juice. Seal and refrigerate for 3 hours.

Drain pickle juice from thighs. Cover chicken; refrigerate until ready to fry or up to 1 day.

Preheat the oven to 350 degrees F (175 degrees C). Set a wire rack over a baking sheet.

Heat 2 inches oil in a Dutch oven over medium-high heat to 350 degrees F (175 degrees C).

Pour buttermilk into a bowl. Combine flour, salt, and pepper in another bowl. Dredge chicken in buttermilk, then toss in flour. Return to buttermilk and toss in flour a second time. Place chicken on the wire rack.

Fill Dutch oven with as many thighs as possible without crowding. Cook in the preheated oil until golden brown, 5 to 7 minutes per side. Transfer thighs to a nonstick baking sheet and repeat until all pieces are fried.

Bake in the preheated oven until no longer pink in the center and the juices run clear, 5 to 8 minutes. An instant-read thermometer inserted into the center should read at least 165 degrees F (74 degrees C).