Stitching on trousers with tapered legs?

Question

I am altering a pair of my husband's chinos which have tapered legs. I want to leave about 3cm in the hem in case of shrinkage over time. How do I stop the fabric from puckering slightly?

Answer 1

Open the seam  a little bit on both sides of the hem allowance before turning up and spread the hem slightly so fabric won't pucker. If there's still puckering open the seam a little bit more and spread.