|I like bias-cut garments very much. I find them flattering for the figure and feminine. My first bias skirt, tried years ago, was a total wadder. I was so depressed that I haven't tried sewing anything on bias until recently this year.
I'm trying to list here a few tips that helped me "tame" the bias-cut garments. Many of them are probably the result of reading various articles but I can't remember any of them so I won't be able to quote.
1) Especially when working with thin slippery fabrics, I use homemade starch to make the fabric as stiff as possible. It's very easy to work with it afterwards. Caution however, from my experience, starched fabrics tend to dry off grain and you have to straighten them when pressing them (before cutting)
2) Staystitch waistlines, necklines, armholes immediately after cutting.
3) Stabilise (I use premade fusible tape or strips of fusible knit) zip openings. A good idea is to center the strips on the seamline and thus your zip won't "poke" (like it does happen in my bias RTW skirts)
4) Stitch the darts (in thin fabrics) using the one-thread technique, which makes the point perfect
5) Sew side seams using a stretch stitch (a narrow zigzag, 0.5 mm width and about 2.5 mm length) and gently stretch the seam while sewing. Therefore:
6) Mark the stitching lines, either with vanishing pencil, chalk or by thread-tracing. If you use your presser foot as a guide and strech while sewing, the seam allowances will appear narrower and when finished and the seam allowances relax, you will discover they are much wider (2.5 cm for instance instead of the 1.5 cm you thought). As a result, the garment will be narrower (especially after hanging) and cling too much to your body
7) Experiment with wider allowances. The excessive ease often drops when the garment hangs, reducing the amount to the standard that you're used to.
8) Normally the bias doesn't fray, so you could leave the seams unfinished. However, satin does fray quite a lot. I prefer to leave the seems unfinished and press them apart. When sewing satin, I serged the allowances together (the finishing needs to be elastic, to have some give, just like the stitching). I haven't tried a Hong Kong finish because I only did thin skirts so far (satin and organza)
9) Always hang the garment overnight. I usufally hang it for 72 hours. You will find out that it gets longer and narrower and your initial hemline gets distorted, the skirt is longer in some places and shorter in others. After hanging, I correct the hemline (use the pattern again), decide the length and sew a narrow hem or I use my serger to do a rolled hem. On my last skirt, I did a scalloped hem and I like it very much.