Clearly you are not unique - I would cut and sew the quilt my way hiding the evidence inside the finished quilt. But when passing my sewn blocks to someone else at Guild - heaven forbid me to show my disgusting seam allowance. So I used what I thought was a precise 1/4" measure. And failed to have the proper block size. In Google I typed "how to get the proper block size" and magically I found an article about finding your personal 1/4" scant seam allowance.
Cut two pieces of fabric 2.5"x 4.5" --- sew using the 1/4" scant seam. Press the seam to one side. Measure. Your newly sewn piece needs to measure 4.5" square.
The way you cut your fabric is also a contributing factor. Placing the acrylic ruler over your fabric (cutting right handed) I try to see the slightest of a sliver of fabric on the left of the line I am using to measure the cut.
I have used these examples in my classes and I feel more confident in passing a sewn block at Guild and less fear when piecing.