01 - Place the chicken pieces in a shallow dish and pour the pickle brine and hot sauce over them. Cover tightly with plastic wrap and refrigerate for at least 2 hours, or up to overnight for deeper flavor penetration.
02 - In a large mixing bowl, whisk together the all-purpose flour, cornstarch, garlic powder, onion powder, smoked paprika, kosher salt, and black pepper until evenly combined.
03 - Remove the chicken from the brine and discard the used brine. Pat each piece thoroughly dry with paper towels. Dredge each chicken piece in the seasoned flour mixture, pressing firmly to ensure an even, adherent coating on all sides.
04 - Heat the vegetable oil in a deep skillet or heavy-bottomed pot to 350°F. Working in batches to avoid overcrowding, carefully lower the coated chicken pieces into the hot oil. Fry for 4 to 6 minutes per side until deeply golden brown and cooked through to an internal temperature of 165°F. Transfer to a paper towel-lined plate to drain.
05 - In a small bowl, stir together the mayonnaise and Dijon mustard until smooth and well blended.
06 - Spread the mayo-mustard sauce generously on both halves of each slider bun. Layer a piece of lettuce, a hot fried chicken piece, and a dill pickle slice on each bottom bun. Cap with the top half of the bun and serve immediately while the chicken is still hot and crispy.