Heat olive oil in a large skillet over medium high heat.
Add fresh spinach, red pepper flakes, and ¼ tsp salt. Saute until wilted. Remove from skillet and set aside.
In the same skillet, add the chicken in one layer. Sprinkle with remaining ¼ tsp salt.
Cook for 5-8 minutes per side, depending on thickness, until done. Set aside.
Add minced garlic, and stir for 1 minute.
Add orange juice, chicken broth, balsamic vinegar, and dried rosemary.
Use a spoon to scrape up any bits of chicken that remain in the skillet.
Simmer until the sauce reduces by about half (should take about 5-10 minutes), stirring often. Remove from heat.
Add the chicken back to the skillet (to reheat a little and soak up some sauce).
Plate the spinach. Top with chicken, and serve with extra sauce. Enjoy!