I do mine on the dining room table by just smoothing it again and again till it is smooth NOT STRETCHED. Then I pin with lots and lots of pins and have never had a problem. Sometimes I find when I try to do things so perfectly I find myself in trouble like you are now having. I have learned to relax.
You will be surprised how great things will turn out when you relax and HAVE FUN with this craft. Hugs and luck go out to you.