I made this top for my son's birthday party.
It's basically a "pillowcase" top style, with cinching at the bottom.
Cording or ribbon, enough to go around your shoulders and waist
Start out with a plain t-shirt, preferable one that's a little big on you.
Cut off the sleeves and the band around the neck.
You could stick with this if you wanted the wife beater look, but maybe we should move on.
Cut the front and back "straps" at the seam.
Now turn under the top to create a casing. If you're using cording, make sure it's wide enough to accommodate it. Do this for both the front and back.
Sew the casing.
Now you have something like this.
Trim the excess on the sides and seams.
Now take your cording or ribbon, and using a safety pin, thread it through your casing.
First the front,
Then the back. You'll have to try it on to adjust the fit. Tie it off and either hide it in the casing or let the tie be part of the top.
To cinch the bottom, we'll use the bottom hem as a casing. Pin where you want the tie to be on the bottom hem.
Cut a small slit on the front of the hem, just big enough to fit your cording through but small enough to fit within the hem.
So you end up with a little slit like this.
Now using your safety pin, thread the cording through all around, and adjust your ties to your liking.
That's all there is to it!
Sorry I don't have better pictures of the end results, this is the best I could do for now.