Worst case, if you consistently end up with 12" instead of 12.5", when you do your cutting, add an extra 1/2" to the pieces. Maybe it's more if you have a lot of seams since each seam reduces your size by 1/4". I'm not really sure how you'd do it exactly - I'd probably draw it out and do some mathy-maneuver to decide how much bigger things would be. But off the top of my head, increasing everything by 1/2" makes sense to me.
Originally Posted by
kensington
This is why I was scouring blocks to see 1. which ones were my skill level or that I would enjoy doing. 2. Blocks that highlight the one main fabric for the sender I will be making blocks for. I challenge myself to do it right. I have made three since last night with my own fabrics to find them. Only one wasn't 12.5, but a perfect 12. Eleanor Burns also always sets the seam when pressing. I did that too. I loved the second and third blocks I did. Each different, but more about the fabric then my sewing skills. Accurate cutting, pressing, pinning and sewing... makes for a lovely block. Even the simple block becomes a welcome addition to your quilt when it's done right.
I think I did see in the rules not to use starch or majic or anything like that because of allergies? I use it on mine, but I don't think I can on those I am shipping back home to their momma's.