In a large bowl, toss together the buttermilk, potatoes, hot sauce, thyme, salt, pepper, mustard powder, garlic, onion, paprika, oregano, and ground thyme until evenly combined. Cover with plastic wrap and chill for at least 30 minutes or up to 2 hours! You don't want anything longer than that or else they'll begin to turn brown.
In a separate bowl, combine the flour, and a large pinch of salt and pepper until evenly incorporated. Optional: Add in about 3 tablespoons of the buttermilk from the potatoes and toss until coarse crumbs are formed. This will give the coating a bit of a crunchier texture when fried.
Working with a few potato slices at a time, carefully remove from the buttermilk (allowing excess to drip off) and place into the seasoned flour. Toss around until evenly coated, and then place on a baking sheet. Continue coating the remaining potatoes until they're all done. Allow to air dry for about 10 minutes to ensure the coating sticks to the potatoes.
Meanwhile, fill a large, heavy-bottom pot, about halfway with oil. Set over medium-high and heat until the temperature reaches 365 degrees F with a deep-fry thermometer. Once hot, carefully drop in a few potatoes at a time and fry until golden brown and crispy on both sides, about 3 to 4 minutes. Remove with a slotted spoon onto a wire rack set over a baking sheet. Keep warm in a preheated 200°F oven while you continue frying the rest. As soon as the potatoes come out of the oil, season lightly with salt.
To make the hot spicy sauce, carefully whisk together the spices, brown sugar, and 3/4 cup of the hot frying oil until dissolved and evenly combined. Immediately pour the sauce over the fried potatoes. Serve with ranch and pickle slices. Enjoy!