Busy Hands Quilts: Custom Twin-Sized Rainbow Wave Quilt Progress #2

Here is my current progress on the custom twin Rainbow Wave Quilt. This quilt is available through my Etsy shop, Busy Hands Quilts.
The white sashings are sewn to the bottom of the rainbow waves, and the sides have been trimmed. Each rainbow wave is created by eight separate pieces for a twin-sized quilt. Their orientation alternates to create the wave pattern, so the white sashing is not sewn on the same side of all eight pieces. You can see that illustrated below.

I am learning some shortcuts to the pattern because this is the third time I have made it. The first change I made is to cut the white strips 1/2" longer so it is certain that they will cover the colored piece when sewing them together without having to be so careful in eye-balling it. Because it is an angled edge, the white piece has to be longer so that it comes out past the colored piece when it is opened and pressed. This extra 1/2" allows me to zip them through the machine without being so careful about how much the white extends over the colored fabric. And it doesn't take any extra fabric; it is only using more of the white WOF strip that would otherwise be scrap.
Another shortcut I have learned is that I really can chain-piece this. The New Wave pattern has you layout the waves on a design wall before adding the white sashing. I have learned to sew the white sashing to ALL of the colored pieces first, without laying it out. I sew a white strip to the "bottom" of four pieces of one color and to the "top" of four pieces of the same color all the while chain stitching them together. I sew the white sashing to the colored piece and then flip the next colored piece over the other direction before sewing on the white sashing, doing this over and over, so white sashings end up on the "bottom" of four pieces and on the "top" of four pieces without having to go back and count because I forgot where I was. I can easily see from the last one I sewed which direction the next one should face. I hope this makes sense!
When using this pattern for the first time, however, I would recommend laying out the pieces before adding the white sashings to be sure you get the hang of it before accidentally sewing them incorrectly and having to rip it out.
The pattern does not address which direction to press the sashing, and I have come up with some guidelines for this, as well. As stated above, I sewed them together alternating the white sashing from "top" to bottom". I then left them in that order when I pressed them. Then every other one from this pile got pressed the opposite direction so the seams will butt together when sewn into columns. This could be stated another way: With the white sashings at the bottom, the four blocks with the wide colored part on the left were pressed one direction, and the four blocks with the wide colored part on the right were pressed the other direction.
Following pressing, I trimmed the white sashings even with the edges of the colored pieces. Once again, my rotating cutting mat was perfect for this. I lined up the four blocks of each color that had the sashings on the same side and trimmed them four at a time, then rotated the mat and trimmed the other side, repeating for all remaining blocks.

Next, I will make eight stacks of the blocks in rainbow order and begin sewing them together in columns - all without ever placing them on a design wall! It takes quite a bit of time getting them up there and then taking them down column by column, so it is nice to have the confidence that this step is not required.