Here is one that finishes at
12".
https://cuddlecatquiltworks.com/blog...ck-12-finished It also has five layers of the tree versus the 4 that you gave. I'm guessing by the measurements that the pattern does have the seam at the tip of the branches. If that is the case, I'm thinking that by making the sides 2 3/4" plus the dimensions given minus 1/2" for the seam allowance will allow you not to have those extra seams at the tips of the branches.
Based on the top and bottom measurements, it looks like this one finishes at 12", also.
http://neighborhoodquiltclub.blogspo...orial.html?m=1