However.......if you are not sure they are all cut accurately, I would make a template from plastic the finished size and use that to make seam marks on the square so at least the finished squares would be accurate. This will take a bit of time in marking/measuring and doing some pinning but I believe you will be more pleased with the outcome. Don't worry about grain/bias. That small a size won't matter. Just measure as you go along and press to get them to lay as flat as possible and maintain the correct size. Scrappy is what you will get and it will be delightful when finished.