When a pattern calls for scant 1/4", I add an 1/8th of an inch on all sides to the rotary cutting and then sew the 1/4 " anyway. I always do a sample first with scraps to make sure the measurement works to the final block size. If not, I adjust it. I do this even though my machine has the needle adjust for scant 1/4". I took 'scant' out of my quilting dictionary a long time ago and I get along just fine.