please, someone correct if this is wrong---my brain does not always figure stuff right.--
you have a 12" fin. block, so each of the interior blocks would be 3"fin on the side. that would make the pink blocks have to be 3 7/8" to cut diagonal & fit the others.
try this on some muslin. remember, you are sewing this bias edge, so pin before you start, so you have the correct amount sticking over the edge.

I am making a quilt for the BOM out of a book I bought from the LQS. Others and myself have found errors from the book while making the quilt. The LQS really didn't want to admit the book had errors but with several of us questioning the book directions, they admitted there were errors. It has been a great learning experience, in that i know it's not always me making the mistake. Pros and Publishers do as well... Can you adjust your triangles to the correct size? I did mine with paper til I got them the right size...

I found the directions for the four at once no waste method of flying geese. The directions are for 2 X 4 inch geese and they use 2 7/8ths inch squares. The directions are here, http://blocksnswaps.blogspot.com/200...ing-geese.html You just sew the seams before you cut on the cutting lines in the pattern.

Your geese finish at 3 X 6 so the squares have to be 3 7/8ths.

The pattern directions have a mistake.

The pattern is in error I think. You need squares of 3 7/8 not 2 7/8. How frustrating this must be for you. Try this new size and see if it doesn't work.

Mistakes in patterns are very common. My LQS owner told me a very interesting story about a fabric manufacturer and their "free" quilt patterns that they have to compliment or show off a new line of fabric. One of her big spender customers who always drops a ton of money had come in and bought all the supplies needed for a quilt. She was using the quilt pattern supplied by the manufacturer. Did all the cutting, got half way threw piecing and then things began to go all wrong. No matter how she tried, the pieces were not going together. Brought things into the shop, they mulled over it for hours with the same results. She even brought it to a guild meeting and the whole group tried to work it out. Still no luck. So finally the store owner called the manufacturer with the problem. She was told that they don't make these quilts, they are published as "complimentary" and they don't make any claims of accuracy. I was shocked to hear this. The cost of all the materials to make a quilt is extremely expensive, even with a sale. These patterns are put out to promote the fabric, I would like to think that they put a little time and effort into delivering a good product. I was very disheartened when I heard this and now I look at all free patterns with hesitation. I can't afford to waste that kind of money and have such disappointment.

Thanks to everyone with suggestions. I am putting it together correctl; I will post a photo soon of the layout on the table. I wish I was better with math and triangles...I have to rely on the correctnes of the pattern so I've always used squares and rectangles. In the "old days" (when I started quilting in mid 1980) I traced the pattern pieces out of magazine onto cardboard, traced the cardboard shape on the fabric, added the seam allowance by eye and didn't have the trouble these directions are giving me! :)

Check out the first method for flying geese in this tutorial:
http://www.connectingthreads.com/tut...hods__D15.html