Preheat your oven to 350 degrees f.
Coat a 2-3 Qt baking dish with cooking oil and set aside.
In a saucepan whisk gluten free flour with milk, garlic and freshly chopped herbs. Place over medium heat and simmer, whisking constantly, until your sauce is thick and bubbly, about 5-7 minutes.
Turn heat off, and allow to cool a bit, then season with sea salt and pepper to taste.
Place the green beans into your prepared baking dish and drizzle your sauce over them.
Toss well to coat.
Transfer dish into your preheated oven and bake for 20-25 minutes.
Top your green bean casserole with crumbled bacon and sprinkle with additional fresh herbs if desired.
Serve hot and enjoy!
Leftovers can be covered and stored in the refrigerator for up to 5 days.