Add the cubed steak to a bowl along with the gluten free flour, salt, pepper, garlic powder, and onion powder and toss to coat.
Heat the olive oil in a large non-stick skillet (or in your slow cooker if you have the saute function) over medium high heat. Add the steak and cook for a minute on all sides until they are starting to brown, but not cooked through. Remove from the pan.
To the same pan, add the butter. Once melted, add in the onions and garlic. Saute for 4-5 minutes until starting to brown and soften. Add in the remaining ingredients except for the arrowroot/water and stir to combine. Add the gravy into the slow cooker (if made on the stove), along with the seared steak bites.
Cook on high for 3-4 hours, or low for 6-8 hours.
Combine the arrowroot powder and water in a small bowl to make a slurry. Turn the slow cooker to high heat. Pour the slurry into the slow cooker and stir. Cook, stirring occasionally, on high heat for 5-7 minutes until the gravy is thickened to your liking.
Serve over mashed potatoes with a side of green beans/carrots and topped with parsley. Enjoy!