I saved the picture to my computer to make my own and set about figuring out the neckline. I tried regular braid. I tried a single strand looped braid.
It didn't look right to me so I set it aside. Eventually I decided that the neckline was not braided, but was a series of single loops, with one loop put through the next and so on. With that decided I was able to get started.
For this project you'll need two plain T-shirts in whatever color you want to make your shirt. One should be your regular size, one should be as big as you can find it. I get mine from Hobby Lobby when they're 50% off. I think they were a large and a 2XL or something like that. You'll also need fabric glue, 1/4" elastic, a seam gauge, a marking pen, scissors and matching thread. A rotary cutter and mat would also be immensely helpful. I apologize in advance for the crappy lighting on some of these pictures.
First, cut the neckline to the depth you want it. If you're using a shirt that has a nice scoopneck already you can probably get away with leaving it. Hobby Lobby T-shirts are too high-necked to leave, though.
To make sure the neck doesn't gape, sew elastic to the wrong side. I stretch it just a little bit as I go.
Then turn that under and stitch again.
If you need to adjust the side seams of your shirt inward, do it now. Hobby Lobby shirts are fairly boxy and I wanted more of a curve to mine, so I tried it on and marked about how much I wanted taken in. It ended up being about an inch per side, I think. I marked mine at my waist. Oh, and remember to turn your shirt inside out before making marks--I had to redo this after I took these pictures because I forgot that step.
Using your seam gauge, make sure the marks are in the same place on each side. I used the sleeve/armpit seam as my starting point here.
Then I put my seam gauge just above that mark and marked 1/8" closer to the edge of the shirt and repeated until I was at the edge of the shirt. Do that going up and down from your original mark.
Now start cutting strips for your loops. I made mine 2" wide and 5" long. This is where the rotary cutter comes in handy. Just fold your second T-shirt in half (side to side) so it fits on your mat. Cut the bottom hem off and use your marking pen to mark off 2", then cut. I think I ended up needing about four yards of strips, maybe six cuts? It didn't use up the entire shirt, I didn't even get to the sleeve seam.
Cut these long strips into 5" lengths.
Time to break out the fabric glue. Fold the edges of the short side of the strip into the center. Put a dot of glue on the first edge that you folded in and put the second edge on top of it. Repeat at the top of the strip. It should now be about 1" by 5". Repeat until you're done with all of your strips. Or if you think you have too many you could do half, glue them to the shirt and come back and do as many more as you need. Set aside two of these strips.
If you have more patience than me, or you think ahead, before cutting the longer strips into 5" lengths you could sew them into long strips, turn and then cut into 5" lengths.
Now it's time to make your loops. Holding the strip with the side with the raw edges down, put a dot of glue at the bottom. Take the top of the strip and turn it so the side with the raw edge is against the dot of glue, like so. Repeat with all loops except the two you set aside.
You shouldn't see any raw edges when looking down at your loop. Or you should only see raw edges. It doesn't really matter as long as yours is turned like the one above.
Start gluing your loops to your shirt. I started in the back, just behind the shoulder seam. This one's right in front of the shoulder seam because I forgot to take a picture of the first one. The tops of your loops should be going toward the back of your shirt.
Glue your first loop down, then measure 1 3/4" from the edge, make a small mark and glue your next loop down. I usually do two marks then glue two loops. Repeat until you have one space left. Don't glue a loop here; glue one of the pieces you set aside. Repeat with your second row. I offset the second row a tiny bit from the first. I like to let the glue dry overnight. You don't have to do this, but I wanted it really set before I started messing with the loops.
And of course I forgot to take a picture of this part, so hopefully I can explain it. Once your glue is dry, starting with the first loop, put it over the second loop. You're going forward, toward the front of the shirt, covering up the raw bottom edges of the loop. Repeat all the way around until you reach the strip that you didn't glue into a loop.
In this picture I'm on the second row, but it's the same procedure for the first row.
Take the strip and put it through the last loop.
Move the strip over to the first loop and put it through.
Put a dot of glue on the side of the strip with the raw edges.
Push it down even with the first raw edge from the same strip.
Repeat for the second row and you're done.
There you have it. If I were to do this again I might make my loops narrower, maybe 1", and not fold them into thirds to reduce a little bulk. I'd also make my neckline a little lower. But all in all, I think it looks great.