Crochet STRAIGHT EDGES in Rows Every Time - Easy Formula for SC, HDC & DC - YouTube
To answer your question, I did not find the video particularly useful. . Her sample in this video is not at all straight-edged, though she claims it is, then says her edges do have "bumps". She says we have to go to her other videos to obtain instructions for her techniques to obtain a straight edge - yet the video here is entitled "Crochet Straight Edges in Rows Every Time".
Getting a straight edge on a single crochet project is easy. The edges come out naturally straight with no effort.
The problems of crooked edges start to occur with DCs. With DC items I learned to use a technique called a "turning single crochet" (a TSC), which is mentioned in the pattern for a shawl that I'm making.
The creator of the above video refers to the TSC technique as stacked single crochets elsewhere on the internet. It is a good technique whatever you call it. I just don't understand why she did not include it in the video here.
I noticed that in the video she she went by how many times you do a yarn over for the stitch you are doing to how many chains you need at the start of a row. For the hdc I ch 2. On the video for the hdc she chains 1 because you yarn over once to finish a hdc.(pulling through the 3 loops on hook once) I ch 2 for a dc - on the video she chains 2 also for a dc because you yarn over twice when finishing the stitch.(pulling through 2 loops twice)
How do you do a TSC?
https://abload.de/img/tsc_stitche9j8i.jpg
This info is from a pattern for a shawl I am working on. I hope this is helpful. I find it useful for any patterns using DCs. You avoid the hole on the side of the row.
They used to say chain 3 for a dc but I've heard that now you can chain 2 for a double crochet but I'll try this method. This is almost like the TSC - Alternative Double Crochet Turning Chain - YouTube
Thanks, Jean Marie, for those videos. I guess I am hard to please, but I simply don't agree with Nicki that her edge on her sample is "extremely pretty," and "all straight", as she says.
She claims she is the one who invented this technique. In any case, these 2 videos should be helpful to everyone. When I first crocheted, ages ago, gaps were a problem but getting a perfectly straight edge seems to be a different challenge.