Fill a large pot with hot water, attach the sous vide cooker, and set the temperature to 168 degrees Fahrenheit (75 degrees Celsius).

Remove any surface fat from the chicken thighs. Place each chicken thigh on a cutting board, cover with plastic wrap, and pound to a uniform 1/2-inch thickness. Lightly salt the meaty side. Repeat with remaining thighs.

Place half the chicken in a large resealable plastic bag, add 1/2 the olive oil, and 1/2 the rosemary. Repeat with remaining thighs, making sure that there is space between the thighs. Use the water immersion method to remove all air from bags. Submerge in the pot and set the timer to 45 minutes.

Once time is up, remove chicken thighs from the pot and dry well with paper towels.

Pour enough avocado oil into a skillet to cover the bottom and heat over medium-high heat. Once oil starts to shimmer, place chicken thighs skin-side down into the skillet and cook until golden, about 5 minutes.