Hong Kong seams are a tidy and very handsome way to finish raw edges... but what happens at the hemline? The seam gets folded up on itself twice, and if you are working with a flimsy fabric and especially if you are planning a narrow hem you will end up with a hem that is thick and blobby with extra fabric; not very attractive.
The solution is to cease the HongKong seaming inside the hem, at a spot before the fabric is folded up into the hem.
With this dress, I had such minimal fabric I couldn't have a deep hem and needed to sew as narrow a hem as pssible. The side seams are French seams which go fine into a narrow hem, but the centre back seam with the zip in it cannot be sewn with French seams obviously, so I opted to finish the raw edges with HongKong seaming... and I took a few photos to show how I dealt with the HongKong seaming into the hem...
The bias strip for the HongKong seaming is sewn to the raw fabric edge, down to roughly 15cm from the lower edge. Then fold the edge of the bias strip over the raw edge, press and stitch in the ditch from the right side to about 10cm short of the first stitching, allowing plenty of tail. I've left the thread ends long and un-snipped to show where I've finished the stitching.
Now insert the zip.
Complete sewing the centre back seam down to the bottom edge.
At this stage, measure and pin the hem, and press it in place. Unpin and unfold the lower hem at the seam.
Trim the bias strip to be just short of the hem fold.
Finish stitching the HongKong binding in place.
Fold up the hem, pin and finish stitching the hem in place.
Voila! The raw edges are all neatly finished, and the hem looks nice and flat with no added bulk too!