Combine the chicken thighs, yogurt, and all-purpose seasoning together in a large bowl. Use your hands to massage the yogurt into the chicken. Make sure each thigh is coated. Cover the bowl and let the chicken marinade in the refrigerator for at least a few hours (overnight is even better).
After the chicken has marinaded, miix together the flour, sea salt, black pepper, garlic powder, onion powder, and cayenne pepper together in a bowl. Whisk to combine.
Add the lard to a large, deep cast iron skillet and preheat the oil to 340 degrees.
Remove the chicken thighs from the marinade and add them into the flour mixture. Use your hands to pack the flour in and around the chicken thigh - this will give you a thick, crispy crust. Repeat with the remaining thighs.
Carefully add the thighs into the hot lard, making sure to not overcrowd the pan. Cook the thighs for 15 minutes (taking care to flip the thighs halfway through the cooking time if they're not fully submerged in the lard). Make sure to maintain at 340 degrees during the entire cooking period.
Remove the thighs to a paper-towel lined plate and repeat until all the chicken is cooked.