if the pattern says cut 4 1/4" and cut into 4- and you cut yours at 4 1/2 that is part of the problem---try the measurements they give you= and trim as you go-
do a 1/4" seam test to make sure your 1/4" seams are accurate- cut 3---1 1/2" x 6" strips- sew them together- and measure the center strip should measure exactly 1"-the whole piece should measure 3 1/2"x6"-- if it does not you should adjust your seam-either wider-or narrower and try again-