It's fairly inexpensive to buy a couple of saw horses and a 4x8' piece of plywood at one of the big box hardware stores. You can set this up on your driveway, and it stores pretty flat in the garage when not needed. I would use clamps with this setup to keep everything straight. Here is a link to the type of clamp I use (on a large table in my sister's community room):
http://www.menards.com/main/tools-ha...914-c-9135.htm
This clamp opens wide and is very easy to fasten and unfasten. Found them in my local Menard's.
Edit: I would add that I heavily starch the backing fabric before layering. This helps reduces wrinkles and puckering a lot. I also spray starch the top before layering.