Preheat oven to 350F. cut a pocket into each chicken breast. Salt & pepper to taste; set aside.
If using fresh spinach steam till wilted and squeeze out juices. With frozen defrost and squeeze out juices(do not cook frozen). Combine spinach, feta cheese, mayo and garlic. Stuff into chicken breasts.
Combine flour and lightly coat stuffed chicken. Wrap 2 pieces of bacon around each and place on a baking rack in a baking dish. Bake uncovered for 1 hour or until chicken tests done.
Note: may be prepared ahead. Cover well; refrigerate or freeze and bake later. If frozen, thaw in refrigerator before baking.