The trim was first to go. I cut the edges above the seams, leaving them raw with no more gray. I was interested in a more fitted and contoured look, so I turned the shirt inside out and used pins to fit the shirt to my hips, waist, and underarms. I removed the shirt and sewed new seams up each side, where I'd pinned. I tried on the shirt to make sure the fit was right, then trimmed the seams (down to 1/4" to 1/2" - to remove the bulk). If you don't want to try pinning the shirt while you're wearing it, use a T-shirt that you already have that fits well and has the same silhouette you're after - just turn your new shirt inside out, lay your existing shirt on top, and pin your new shirt to follow the seams of your old shirt.
I didn't want to leave the edges raw, but I also didn't want to go to the trouble of hemming all the edges. So, I decided to do a lettuce edge using a zigzag stitch along the edges. The trick is to set your machine to the widest zigzag, a short stitch, and then stretch the fabric as you sew. Sew this zigzag right on the edge. The more you stretch the fabric, the more ruffle you get along the edge. I personally like a contrasting thread for the lettuce edge, so I just used an off-white thread for my orange shirt.
Finally, I wanted something to do something to make the T-shirt prettier. I had some beautiful fabric that matched the orange shirt and also added a splash of vibrant colors. I sewed a few pieces together, forming a narrow tube scarf. You could also use an existing scarf, a ribbon, or any piece of narrow fabric. I started in the middle back of the shirt and cut two holes in the shirt, roughly an inch or so apart from each other, and a couple of inches down from the edge. I then cut pairs of similar holes every few inches, going around the neckline, each pair a couple of inches down from the edge. My motto is that I avoid measuring whenever possible, and most of the time it works out fine. I like to just use my fingers to do a rough measure to try to evenly space, but if you're more of a perfectionist, you could measure the neckline to ensure your cuts are evenly spaced.
Once I had my pairs of holes cut, I wove the scarf through the holes and gathered it gently to pull in the neckline. Since I'd cut the neckline away, this pulled it back up to avoid the Flashdance off-the-shoulder look (fine for many, just not for me). The T-shirt material shouldn't unravel or tear where it's cut, but if you have a particularly fragile piece of fabric and are worried about fraying, you could finish the cuts with Fray Check prior to adding the scarf.
The scarf can be tied in a knot, bow, or just left hanging, to change up the look a little. If your scarf is washable, it can be left as is for laundry. If not, just remove it prior to washing.
I really like the end result. Here are the pictures!
