I think bias-cut garments are so flattering. They hug the body through the hips, then flair out at the hemline. They are comfortable to wear as well, bending with your elbow when used for sleeves or with your knees when used for a long skirt. Awhile back, after several failed bias-cut garments, I figured out an easy way to get perfect seams, and I thought I would share it with you. I don't know if there are easier ways of achieving this technique or not; I've never really researched it. This is just my way, and it's pretty simple.
1. Start with approximately 1" strips of tissue paper. I write approximately because I just eyeball it.
2. Now measure against your pattern. In this example, I am sewing the back seam of a dress with a bias skirt. I'm starting at the marked spot for the zipper and measuring down to the bottom. If one strip of tissue paper isn't long enough, you can tape two strips together with scotch tape.
3. Now put yourself a mark on the bottom. STOP! Do not cut yet. For some reason, bias garments hang better if you allow a little bit of stretch to the seams. In a sleeve I'd allow about 1/2" extra of tissue paper, in this skirt it was around 3/4", for a long skirt maybe 1 1/4". Now you can cut off the excess.
4. Pin your garment together. Line up any markings and make sure the sides are neat.
5. Now give yourself some room to stretch out. Pin your tissue paper strip to the top and bottom. I'm starting at the clip I made for the zipper and finishing at the bottom hem. It may look a little stretched out right now. That is okay.
6. Now, starting in the middle, pin the tissue paper to the fabric, trying to smooth out any bumps or fabric excess. Don't be afraid to use lots of pins! Take your time, and make sure the sides are neat and straight.
7. Now stitch. You are stitching on the tissue paper, so it won't stretch out. You do have to be a little careful using this method. Tissue paper does tear easily.
8. Okay, you want to carefully tear the strip away from the stitches on one side. If you go slow this should be pretty easy and neat. If you've used scotch tape to join two strips, cut the tape with scissors as close to the stitches as possible.
9. Now the other side should come off with little effort.
10. Give it a good pressing. And... Voila! Now wasn't that easy?