If things have really gone to hell in a hand cart, I use a method which I jokingly call "The great quilters art of fudging" :lol: Is helpful when sewing rows of blocks tog especially if you've got the blocks from a block swap or guild BOM.
First of all I match up the seams and do a couple of machine bast stitches to hold, open out and check match is correct. Then I sew the seam putting the bigger block on the underneath, the action of the feed dogs has the effect of slightly gathering the underneath fabric, If when I get to the next seam the larger block is on the top I just take the sewing out of the machine, turn it over and stitch in the opposit direction. Keep doing ths untill the entire row is sewn. Can get rid of up to a 1/4" per full size block, anything more and you gonna have a frill :lol:
Another way if things are really bad is to add a boarder to each block and then trim blocks to an exact size. A crazy boader is nice, where the blocks end up looking tilted.