Put flour into a clean brown paper grocery bag, generously season with salt and pepper, and set aside. Pour oil into a large cast-iron skillet or a medium cast-iron pot to a depth of 1" and heat over medium-high heat until temperature reaches 350º on a candy thermometer.
Meanwhile, rinse chickens (do not pat dry), then cut each into 10 pieces. Shake 1 piece of chicken at a time in the seasoned flour in the bag until well coated.
Working in batches to avoid crowding the skillet, fry chicken in hot oil, skin side up, largest pieces first, turning once, until skin is golden and crisp and juices run clear when chicken is pierced with the tip of a small sharp knife, about 8 minutes per side.
Drain chicken on wire racks set over brown paper grocery bags (Reserve 3-4 tbsp. of the frying oil and crisped floury bits from the bottom of skillet to make gravy, if you like. Serve hot, at room temperature , or cold.