Beautiful quilt top and I agree with dunster. JMHO

Take a ruler and line it up against every other row. That should show you where you are off. What I would probably do is simply adjust and cut off whatever doesn't line up at the ends.

If you are duty-bound to take all the rows apart, you can likely avoid the issue by using a pencil and ruler on the wrong side of the sashing strips to mark where every block starts and ends. These become your "virtual" seamlines for lining up. Pin top row with sashing to next row, matching actual seam lines with virtual seamlines that were marked on the top sashing, then sew. Do the same for each subsequent row. You need to ease or stretch the seams when you sew in order to get the pins to match. If you don't do this, chances are when you sew all the rows together again you will still get uneven edges.

If you stretch or ease in the rows, you will get cups in the quilt that will have to be quilted out. We ease in and stretch to fit clothing, not quilts. If you are constructing a quilt in rows, measure each row and make sure they are all the same before pinning together and sewing. If the little bit on the bottom is the problem, take that row off and measure the rest, then adjust that row to the same measurement and re-attach. I think the design is wonderful. You might just want to square up the top as it is now, and add a border of the white fabric all the way around.

When there are long sashing borders like this it helps to use a walking foot or an even feed foot engaged to help keep everything moving the same through the feed dogs. It is very easy to get off if you don't. I also pin like dunster does so I know it is aligned before beginning the stitching.

I have to respectfully disagree with the statement that we don't ease when quilting. If we all sewed perfectly then there would be no need to ease anything, but the reality is that we frequently ease the borders or rows, and this does not result in a cup in the finished quilt. I'm not suggesting that you try to ease when there is a large discrepancy in size, but if it's a small difference then it's a common and necessary practice.

I have to ease in borders or my quilt top will wave. If you ever sewn in sleeves when making clothes, you know you have to ease to get a smooth seam. It really helps to know basic sewing skills.

First of all I don't see where it is uneven from the picture. When there is sashing in a quilt it is easy to get things going askew because of stretching. Whenever I do sashing I do it the same as I do borders. Measure the center (in this case the block) and use that measurement and then ease in to fit. I too disagree that you don't ease in quilting making. I have to do some easing all the time with my border and sashing. In the end I have flat square quilts. Sometimes it takes a lot of pinning to get things to fit but in the end I'm happy with the results. After I measure I mark my center spot and then the quarter way spots on both the quilt and the shashing/border and match those spots and then ease in between. Sometimes I will even mark the eighth way spots if the distance I'm covering is long. For me making a quilt with sashing is challenging. Another way to diminish the problem of stretching is to make your sashing with corner squares. If you want a continuous look just make your corner squares the same fabric as the sashing. This way you have less distance to match.

I think you're being too hard on yourself.

I have never seen a recipient measure a quilt. If it is not very noticeable I would leave it. If you feel you cannot do that, see of you can adjust it with a border. Chalk it up to tuition, the price of learning!

I agree. I have to add more. The computer police said my message is too short. Other than the short white on the bottom, I can't see anything.

First, yes, I have done this more times than I can count. Second, it is lovely, and third I agree with Dunster about how to fix this. You can do it!