Yes that's the book!
Another thing to think about. Too late for this quilt, however, is to oversize the triangles on the edges so that they extend half inch or so beyond the petals. then you could make some short vertical seams to join the edges of the triangles. This would give you a small border around the quilt and could attach the binding to that.

For the larger version, I would not cut the outer squares off to triangles. They could be trimmed to 1" beyond the edge of the quilt, the excess pressed in half, then folded to the back like a single-fold binding to finish the edge. If you cut them larger (sort of like oversizing a setting triangle), then the corners will overlap, and you can seam them together to get a continuous bias binding.

For this little one, you could use bias tape to finish it. It will give a finished edge with less bulk than a double-fold binging. A satin stitch would also work.

What to you plan to do with this sample? If it was mine, I would look at getting a picture frame and displaying it that way - I think it's gorgeous! You could use a dark frame with a white or cream mat; this would give the white border look that a couple people have mentioned. You might have to put some batting behind the mat to get it to sit correctly, and I probably wouldn't use glass in front of it.

Interesting method that I had not thought of. I may take out the stitching on the outside windows of this sample and replace the triangle fabric with larger triangle fabric to see how it would work.

I think a 3rd fabric would be best anyway. The same as the windows, would not let the windows show to their best advantage. I would start by auditioning with a tonal blender of the same as the darker shade in your cream print fabric.

As some have suggested, you could stitch the piece you have now, down to the background/border fabric with the raw edge exposed. That would mean you would have a double row of stitching. Personally, I don't care for seeing the raw edge, but that is just me. Especially when it is such a beautifully done piece. Although, you maybe don't have much choice, as to seam it, even an 1/8", you are going to cut off some of the edge of the perfection you have achieved.

Binding, I think I would stick with a knife edge ....... clean and does not detract from the beauty of the windows.

I am working on a Cathedral Window quilt and don't have the raw edges. What technique did you use for yours? Mine is like this one:
http://www.quiltingboard.com/tutorials-f10/machine-stitched-cathedral-window-tutorial-t35742.html

As you can see it does not leave raw edges but a folded edge. I also did a "test run" and made my sample into a pillow but yours would be beautiful framed as Jennifer23 suggested, then you would not have to worry about the edges. I also am doing the "windows" by hand, not sure if I will ever get a quilt or not, maybe a bed runner. Wish I had done it by machine now that I am so far into it.
Love your colors.

I started with this YouTube Video: https://www.youtube.com/watch?v=2u8AT6lJK_c&t=191s
In this version the half-square triangles on the outside are raw edges. I also added batting and backing. If I left off those things, my cathedral window wouldn't have raw edges to bind like yours.

OK, now for plan C (or are we up to D or E?). What if first, before adding the triangles around the edge you trimmed the backing & batting flush with the folded edge of your background fabric. Then instead of triangles, use squares a bit larger than the ones in the center of the quilt. Before inserting them, turn 2 adjacent sides in 1/4" and press well. Now put the raw edge corner into the window, stitch as usual, then turn the loose part of the square to the back & hand stitch down. This will bind the edge and give you an interesting look on the back too.
Hope to see a pic of the idea that works best!

I like this idea, however, I would probably use invisible thread so as not to detract from the design. I prefer edges finished in some way.

Excellent job! I am no help with the binding though.

Wow! If you are able to get those outside triangles larger, that would be the way to go. A very much lot of work, but your finished product would be sooooo much better. I can't figure out how you can do this, but maybe you can.

The only other way I could figure out would be to sew a single layer of binding strip to the front with a very small seam and follow the curve and then into the triangles a little. Then turn that binding to the back as if it were a facing, but a very small line of it will show on the front, also. You'd have to stitch that from the back, following your lines of sewing on the front that you can see. Or make a line of sewing there to follow from the back.