Make the marinade Whisk together olive oil, lemon juice, lemon zest, minced garlic, thyme, rosemary, oregano, salt, pepper, and smoked paprika in a small bowl until combined. The marinade should smell strongly of lemon and herbs - that is what you want.
Pound the chicken Place chicken breasts between two sheets of plastic wrap. Pound the thicker end down to an even three-quarter inch thickness using a meat mallet or rolling pin. Even thickness means even cooking - the thinner end will not dry out while the thicker middle finishes.
Marinate Place chicken in a gallon zip-top bag. Pour marinade over, press out air, seal, and massage until all surfaces are coated. Refrigerate for 30 minutes minimum and up to 2 hours maximum. Do not go beyond 3 hours - the lemon acid will begin to make the texture mushy.
Remove and dry Remove chicken from marinade and pat each piece completely dry with paper towels on both sides. Surface moisture creates steam in the pan and prevents browning. The flavor has already penetrated - the liquid on the surface is not needed.
Sear the chicken Heat avocado oil in a large skillet over medium-high heat until shimmering. Add chicken in a single layer - do not crowd the pan. Cook undisturbed for 5 to 6 minutes until the bottom is golden brown. Flip and cook another 4 to 5 minutes.
Check temperature Check internal temperature at the thickest point. Pull lemon herb chicken from the heat at 160F - carryover cooking will bring it to 165F during resting. Do not wait for 165F on the thermometer or it will arrive at 168 to 170F and be drier than it should be.
Rest Rest chicken in the pan or on a plate for 5 minutes before cutting. This allows the juices that moved toward the center during cooking to redistribute back through the meat.
Finish and serve Sprinkle fresh parsley over the rested lemon herb chicken immediately before serving. Add lemon wedges on the side for squeezing at the table. The fresh parsley and lemon at the end restore the bright herb character that cooking mellows slightly.