Place chicken in a large bowl with a cover. Pour the pickle brine over the chicken, turning to coat each piece completely.
Allow to brine overnight and up to 24 hours. Brining really impacts the tenderness of your protein, so brining it longer will only mean juicier results.
To fry the chicken:
When ready to fry the chicken, pour your oil in a large Dutch oven pan set over medium heat. Place your thermometer in the pan, and heat the oil until it reaches 350 degrees.
Pour buttermilk in a large bowl and add dried dill and cayenne pepper. Which to combine. Place flour on a large plate and top with cracked pepper.
Dredge the chicken in the buttermilk mixture, and then toss in the flour. Really make sure that they're covered! Repeat this process (buttermilk then flour) one more time before placing the chicken in the hot oil.
Cook the chicken, flipping every so often to promote even frying, for about 8 minutes, or until the chicken registers at 165 degrees when probed with a thermometer.
To make the dill pickle slaw:
Combine the mayonnaise, pickle brine, dill, salt, and pepper in a large bowl. Whisk to combine.
Add shredded cabbage and toss to combine.
To assemble sandwiches:
Spread the top of each bun with mayonnaise. Place one fried chicken thigh on the bottom of each bun and top with dill pickle slaw and sliced pickles.