Preheat oven to 400 degrees F. Prepare a large baking sheet by spraying with cooking spray. I actually line my baking sheet with foil and then spray with cooking spray.
In a frying pan on medium heat, heat olive oil until hot. Then add onion, garlic, salt, pepper, thyme, oregano, and red pepper flakes. Sauté until onion is tender (about 5-6 minutes total time).
Add spinach to pan and combine with onion mixture. Add Worcestershire sauce and chicken broth and mix well to combine. Cook until most of the liquid has cooked out (evaporated). I don't have much liquid in my pan after I combine all these, but it will depend on how well you drained your spinach. Remove from heat and allow to cool to room temperature.
In a large bowl, combine the turkey, bread crumbs, and egg. Add cooled onion/spinach mixture to the meat. I do all of this step with my hands, but you can use a spoon if you prefer.
With your hands, create meatballs that are about 1 - 1 1/2 inches in diameter and place them on the baking sheet. Leave a little bit of space between each meatball. When you are done shaping your meatballs, you will probably have about 40-42 meatballs from this recipe. Don't need that many? Freeze them after baking or cut this recipe in half (but I say freeze them and then you've done the work only once and have a future meal).
Bake until your meatballs are cooked through with an internal temperature of 160 degrees F - which was about 20 minutes for my oven. Remove from oven and serve as desired.