Preheat the oven to 425 degrees Fahrenheit.
Remove the chicken from its packaging and remove the organ meats that are inside the cavity. You can cook these organ meats separately, or you can discard them. Transfer the chicken to a large casserole dish, roasting pan, or to a baking sheet.
Melt the butter in the microwave, then stir in the avocado oil, fresh garlic, herbs, and sea salt.
Use a spoon to get underneath the skin so that you can easily distribute the garlic herb butter mixture between the skin and the muscle. The skin should peel away easily without much effort.
Scoop a generous amount of the garlic butter mixture underneath the skin so that it’s covering much of the breast.
Pour the rest of the garlic butter mixture over the whole surface of the chicken. Stuff the cavity of the chicken with the sliced lemon and use kitchen twine to tie the legs together (if you have it. If not, leave the legs untied).
Place the chicken on the center rack of the preheated oven and roast for 40 minutes. Remove the chicken from the oven and baste it using a spoon or baster, ensuring you cover the whole surface liberally with the juices.
Move the oven rack to the bottom shelf (so that the chicken will be farther away from the top heating element) and place it back in the oven for another 30 to 40 minutes, or until the internal temperature of the chicken reaches 165 degrees F. For the best results, use a meat thermometer to check the internal temperature.
Once the chicken is finished, remove it from the oven and allow it to rest for at least 20 minutes before slicing into it. During this time, you can continue basting it if you’d like.
Serve roasted chicken with your choice of side dishes, and enjoy!