Some times when assembling a quilt top with squares that I have made, I have problems. Problems making the individual squares line up and match at the corners. Remember, I am not that experienced; but I am a wee bit sloppy when it comes to cutting and sewing. I have learned that I can no longer apply the old carpenters saying "if it's close - nail it". I have learned that in quilting "close" is not enough. But still, I some times end up with some squares that just don't "measure up". Some one once told me the secret was to just stretch the squares and "pin the snot" out of them to assemble. I soon learned that that was no substitute for accuracy.
My solution was to make the squares a wee bit over sized and then use a template of the finished square size and trim all the squares. In this manner all the finished squares are exactly the same size. If you try this, make the template out of plexiglas so you can see through it to line it up to trim the squares. This technique will not work on some squares in which there are more than just the corners to match up. But it does work with the log cabin square. You just have to cut the last (outside) logs a wee bit wider (1/2 inch).
But, as I have been reminded, there is no substitute for accuracy, and accuracy comes with practice and experience. Or put in another way: practice, practice, practice....and practice!