There are different terms and ideas used with "floating" Looking at the quilt in question, I think what you want is pretty easy.
You need two long rectangles, each maybe 2" longer than your desired finished size. The wider the rectangle, the more the block will tilt. Then you want to use a partial seam on your first row, put the wide corner on one end and sew about half way.
I really like the look of those blocks going up and down but when I made my own similar project, I didn't double check the instructions and I ended up flattening out the rows but it still gives the overall look I wanted and nobody know but me and the people I tell it isn't exactly as planned.
Edit: Added another project done this past year as a comfort quilt. We used a book for that one too but I don't remember the name. I do remember the book had a wonderful method for how much to add and it worked out mathematically beautifully! I'll have to ask the name.
I'm pretty sure the idea for my quilt came from Karla Alexander's first Stack the Deck book, might have been another one in that series.
https://www.goodreads.com/book/show/...tack_the_Deck_