This weekend I made a very simply t-shirt recon. Here is the tutorial:
1- Cut the t-shirt as I show in the next picture. As you can see, you have the pattern of the t-shirt (the front and the back, in dotted line) and two strips. You will need the entire strip number 2, and only the half (or even less) of the strip number 3.
2- Sew the 3 pieces as I show in the second picture. This is, the strip number 3 will be the central part of the front, and sew the strip number 2 to the back, to both sides of the front and then sew its extremes. This strip will pass behind your neck.
3- Finally, gather the neck in its central part. This is the result: