Originally Posted by
Tartan
I would get out some construction paper and cut the pieces without seam allowances. I would trim the paper squares until I got my desired border size. I would then add the seam allowances and figure out my fabric squares.
Ditto to Tartan ... I would draw it out on paper or use construction paper, minus seam allowances.
Then once I thought I had it figured out, I would try it with fabric (remember to add the seam allowances) ... but not my quilt fabric, just in case my calculations were wrong!