Take off the t-shirt and lay it on the floor once more, lining up the front and back edges where you cut. Fold it in half armhole-to-armhole and make sure that your chalk marks are even. If one is off a half inch or so, don’t sweat it, just adjust it to match the other one. Unfold the shirt again so that it is laying flat on the floor.
If you are using a pair of scissors for this step, you’ll need to be careful that you don’t poke yourself. When you make holes, don’t stab through the fabric, instead cut little 1/8” slits through both sides of the fabric. Start your first cut on your chalk line and finish up at the bottom, making your slits one to two inches apart.
(Optional) Grommet Punch: If you chose to use a grommet punch, then this step is going to take a matter of seconds. Grommet punches are cheap and can be found at the craft store or your local Wal-Mart. Start at your chalk mark and use your grommet punch to make holes either an inch or two inches apart all the way to the bottom. Make sure you are punching through both the front and back of the shirt.
Once your holes are in place, you can start to lace up the sides.