Originally Posted by
knlsmith
If you just cut sew then trim you will risk having wavy borders, possibly bad enough they will need re-done before quilting. The best practice (not the quilt police, just saying IMHO) is to measure the top, middle and bottom. Then average that to get the length for side borders. then after those borders are on, measure the left, middle then right side. Average this and you will have your top and bottom borders. (You can do top or sides first your choice). I also round down to the nearest 1/8th inch instead of up. I have never had a wavy border doing it this way. When I first started, I didn't know about this process, and had to redo a couple quilts because I would have had to pleat the borders to make them fit. Wouldn't have been the most pleasing look.
I agree with knismith, well said. However, I suggest to my quilt students that if the quilt is a rectangle, add the side borders first, then the top and bottom. If you do the top and bottom first, you end up with very long side pieces. Doing the sides first creates an impression of the quilt looking a bit more square. (It's sort of like why tall, thin girls don't wear vertical stripes, and why we chubby girls don't wear horizontal stripes.) Also, depending on the amount of border fabric you have, it may be more practical not to have to try to cut very long pieces for the long sides if you do them last. So, sides first.