After many a lace shawl became unsatisfactorily blocked using this process, I devised a system for blocking aggressively without investing in a blocking table (or hauling myself down to Target to get a ginormous piece of cardboard to do it on.)
Hence the lawn-as-blocking table technique was born. I tried this a few times, using straight pins, and found that the wind kept knocking the pins out of the ground. Finally, I decided, screw it, I'll just use knitting needles.
Hence, I am now (re)blocking my shawl thusly.
After soaking your shawl in warm water, take a couple of towels outside onto this grass (this really only works when the ground is clean, so obviously as winter comes I'll have to devise something new). Lay them out, covering enough ground to stretch the shawl as far as you want it to go.
Start by stabbing the shawl in the central increases yarn overs, to hold it into place. Then, using straight, metal needles (of which I have many) start placing them in lacy sections of the shawl that you want to stretch. I started by stabbing a few in the corners (since this was a triangular shawl...have yet to make a circular shawl and test this out). Then I started along the top edge and bottom border, placing the needles in places where they wouldn't disrupt the yarn or pattern (such as yarn over holes). I kept doing this around the length of the shawl, till it was in a satisfactory shape and size for my tastes. Lace weight yarn dries *really* quickly in the sun, so I suggest continuing to wet it with a wet washcloth as you go along, so as not to tear the yarn. Since the needles are metal, long, and hard (lol) you can stab them straight through the towel and into the ground far enough to securely hold it in place. This is working infinitely better for me than straight pins on *any* surface has so far.
I took a few pictures, which I'll post tonight, but I wanted to write this out before I forgot. This is so much better than any other method I've done.