I did the same kind of calculation for the corner sections. And then came the tricky bit - small applique circles (I drew around the base of an Aurifil spool) and bias strip stems (3/8" wide).
So I enlisted some online help from Sarah Fielke to make both the miniature applique circles:
... and the bias tape and hey presto, month 1 of the BOM is done and under my belt without too many tears.
If you want to learn more from Sarah, check out her Craftsy class here: