I have a mock turtleneck that I picked up for about a dollar somewhere. I didn't wear it much because I didn't like the feel of the collar around my neck; as a highly sensitive person, totally comfortable clothing is very important to me. The shirt does have a good length; most women's shirts are shorter than I like.
Today I wore that shirt, and got so annoyed by it that the first chance I got, I took a piece of chalk, drew a new neckline in the mirror, and cut and sewed the shirt. For sewing, I folded over the edge and hand stitched with some thin linen yarn (from my mother-in-law, of course). I started with sort of a zigzag stitch, but switched to backstitch for the front.
The stitch came out somewhat imperfect, because I was in a hurry, but I was mainly aiming for comfortable. The yarn is a light sage green in the skein, but looks like more of a bilious yellow against the shirt fabric. Either color goes well with the rest of my wardrobe.