Ruth! It worked!
I just tossed it out on the walk (after sweeping the gunk off the walk 8) ) and left it out there for a few hours - and it got flat!
I brought it in and put it on the table where it would stay flat and laid a board and weight on top of it until it cooled off - looks great...
thanks a million - as I said, I tried the 'wet towel and iron' - probably didn't get it hot enough or something....