|My armhole called for 3/8 inch seams, so I cut a bias strip 1-1/4 inches wide and at least 2 inches longer than area to be bound. (For some reason the band is always narrower than anticipated, so I always make the strip at least 1/8 inch wider.) I pressed down 3/8 inches along one long end. Then I stitched the band to the right side of the armhole 1/4 inch from the raw edge. I then trimmed the seam to approximately 1/8 inch and turned the folded edge to the inside (if I were binding a neck edge, here is where I would trim and turn in the ends and enclose them before turning under the folded edge).
Using a slightly longer stitch length, I then stitched along the seam line on the outside, holding the band firmly along the edge of the armhole so that the band is caught on the inside. I used two rows of straight stitching because I had already applied a neckband and was matching it (I had added a second row to hold it down).
The bias band could be stitched with a twin needle or with a zigzag stitch..
In this instance, I then sewed the side seams (it is easier to line up the edges of the binding if you sew from the bottom and end up with the bias strips rather than starting with them). I then serged the seams, cut off most of the serging tail and tucked the rest inside the seam and tacked it down by hand where the binding overlapped since it would be difficult to sew through all these thicknesses by machine.