We screw them down into the field using a thick dowel through the eyelet as a handle. One source of inexpensive stakes is half-inch rebar available at most hardware stores. On any surface, you can use cars with bumper hitches. Yes, anchor the line first. Let the anchor do the work for you.
Large kites pull hard.
You need the safety of being already tied down before you try to launch. With the line anchored, you can concentrate on opening your sail. That's not good. Large foils should only be launched after good, solid anchors are secured, the flying zone is assessed for potential problems, and the line is secured and laid out between the anchor and the kite. Ideally, three people should be used.