HeartStrings blocks are pieced on a 10 inch foundation block and are squared to 9.5 inches after the foundation is covered with strings.
I square my blocks from the back.
I will be trimming from all 4 sides of the block so for my first cut, I’m going to cut about 1/4 inch off the foundation from the top and the right side. Notice that the diagonal line on my ruler is running down my center strip.
Before I cut, I double check that my foundation extends beyond the 9.5 marks on the bottom and the left side of the block.
I trim up the right side and across the top.
I flip my block around.
And using the ruler to measure exactly 9.5 inches, I trim the remaining two sides.
Here’s my 9.5 inch block.