Preheat your oven to 400°F and line a baking sheet with parchment paper.
Slice the spaghetti squash in half lengthwise, scoop out the seeds, and roast face down for 40-45 minutes until the flesh is tender.
While the squash roasts, season the chicken breast with half of the sea salt and black pepper.
Heat a skillet over medium-high heat and sear the chicken for 6-7 minutes per side until fully cooked, then slice into thin strips.
In the same skillet, reduce heat to medium and add the olive oil, minced garlic, oregano, and the remaining salt and pepper.
Sauté the garlic for 1-2 minutes until golden and aromatic, then add the baby spinach and cook until just wilted.
Use a fork to scrape the roasted spaghetti squash into long strands and add them directly into the skillet.
Toss the squash with the garlic oil and spinach, then fold in the sliced chicken and fresh parsley.
Plate the dish and finish with a sprinkle of grated parmesan cheese.