I've used the same three plastic tarps as drift socks for years, being frustrated with what's available commercially. Nylon rope tied at each corner, long enough to gather and tie to a ring in center when laid flat. Large snap swivel at the end of main rope allows for easy interchangeability between my small, medium, or large one, depending on wind conditions. I usually throw it out, and give it a tug with the boat to fully deploy.
I do the same as Carolina Partimer, using a 10' x 10' plastic tarp with foam floats on 2 corners and 2 - 1 oz sinkers on bottom corners. I don't think I've ever gotten above .5 mph, even when winds blowing pretty strong. I also put carabiner clips on each corner, as I am a real pro at getting the ropes twisted up in knots. Simply undo each corner and untangle the ropes and reattach. When picking it up only grab one rope and pull in by one corner, it will collapse pretty easy. Trying to pull all ropes at once is almost impossible to lift, I also use a large swivel in line to avoid twists