I starch all my fabric before cutting. Never starched during of after sewing.
But I understand some do.
For pre-cuts, I adjust my cutting/sewing to the size of the pre-cuts after
starching/ironing. For charms, I prefer to make patterns that use 4.5" squares
that way I'm covered for any shrinkage and I can trim my charms to 4.5"
and avoid the pinked edges. For layer cakes I go with max 9.5" squares.
For jelly rolls I use them as is...no trimming.
But I have to adjust my 1/4" seam allowance once/twice.