Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
Wash and dice the russet potato into 1/2-inch cubes.
In a small bowl, toss the potato cubes with 0.5 tsp of olive oil and a pinch of the sea salt, black pepper, and garlic powder.
Spread the potatoes in a single layer on one side of the prepared baking sheet.
Rub the chicken breast with the remaining 0.5 tsp of olive oil, lemon juice, dried oregano, and the remaining sea salt, black pepper, and garlic powder.
Place the chicken breast on the other side of the baking sheet.
Roast for 20 to 25 minutes, or until the chicken reaches an internal temperature of 165°F and the potatoes are fork-tender and golden.
Remove from the oven and let the chicken rest for 5 minutes before slicing.
Slice the avocado and serve it alongside the roasted chicken and potatoes.