Combine salt, pepper, smoked paprika, garlic powder, onion powder, oregano, basil, thyme, cayenne pepper, and brown sugar in a small bowl. Stir well to evenly distribute all spices. I like to make this spice blend in advance because it ensures the spices are fully incorporated and ready to coat the chicken evenly without any clumping.
Cut the chicken into 1-inch chunks for even cooking and uniform searing. Place the chicken pieces in a bowl and pour the spice blend from Step 1 over them. Toss thoroughly, making sure every piece is well-coated with the spices. This step is crucial—each bite should have that signature blackened crust, so don't rush the coating process.
Heat olive oil in a large skillet over medium-high heat until it shimmers, about 1-2 minutes. Working in batches if necessary to avoid overcrowding, add the spiced chicken pieces and cook undisturbed for 2-3 minutes until a dark crust forms on the bottom. Flip each piece and cook for another 3-4 minutes until the internal temperature reaches 165°F when checked with a meat thermometer. I recommend checking a few pieces to ensure they're cooked through, especially the thickest chunks, since uneven pieces can cook at different rates.