Put the chicken pieces into a large bowl. Cover the chicken with water by 1 inch; add 1 tablespoon of salt for every quart of water. Cover and refrigerate at least 2 hours and up to overnight.
In a large shallow platter, mix the flour, garlic powder, onion powder, paprika and cayenne until well blended; season generously with salt and black pepper.
In another platter combine the buttermilk and chili sauce with a fork and season with salt and black pepper.
Drain the chicken and pat it dry. Dredge the pieces, a few at a time, in the buttermilk and then dip them in the seasoned flour. Let the chicken rest while you prepare the oil.
Fill a large deep pot about three-quarters full with the oil. Add the garlic, sage, thyme and rosemary to the cool oil and heat over medium-high heat until the oil registers 175°C on a deep-fry thermometer.
(The herbs and garlic will perfume the oil with their flavor as the oil comes up to temperature.)
Working in batches of 3 to 4 pieces at a time, carefully add the chicken to the pot and fry, turning once, until golden brown and cooked through, about 12 minutes.
Remove the chicken and herbs from the pot with a big skimmer, shaking off as much oil as you can, and put them on a tea towel or brown paper bag to soak up the oil.
Sprinkle all over with salt and a dusting of black pepper. Repeat with the remaining chicken pieces. Scatter the fried herbs and garlic over the chicken.
Serve hot with lemon wedges.