A flat squared quilt starts in the beginning. I starch the fabric before cutting. I know where my 1/4" is. When I'm finished with a top, if it is 76" across the top, it is 76" across the middle, 76" across the bottom.
But blocking the quilt when finished is a good way to flatten them.
I've seen some very wavy borders in big shows too though, quilting is a learning process and I've honed my skills starting with admiring what others have done. Just finishing a quilt is progress!
and I love seeing all levels of skill in shows. And honest, the only quilt police that exist are in our own head, don't measure yourself against others.
There are specific guidelines/point system quilt judges follow, here are a few.
some of the “measurable” criteria judges use to evaluate quilts in competition:
Are blocks square? Is the quilt square?
Are points in the piecing chopped off? Do the intersections line up?
Are borders straight?
Does the quilt edge wave or ripple?
Are piecing threads showing?
Do seams shadow through light fabric?
Are quilting lines straight?
If gridwork is used, is it parallel and straight?
Are curved stitching lines (or applique edges) smooth?
Can you see any starts and stops?
Can you feel any knots on the quilt back?
Is the tension generally balanced?
Is the stitch length consistent?
Is the quilting density balanced through the entire quilt design?
Is back-tracking done well?