Cut off the closed-end of the pillowcase. (I wanted to use the already open end for the bottom edge of shirt). Then, I folded the cut edge over and cut off about 8" of extra fabric length. "Try it on" first to see how long you'd like to keep of the length, and safety pin.
Then, fold the top edge down about 2 1/2" from the top and then make a casing (about 1 1/2" wide). Make the casing pretty large if you also choose to use a piece of 1"elastic (I had leftover) in the back gathering part. Next, sew around the casing lower edge, leaving an opening at both side seams to slip the elastic into.
Sew top edge of casing about 1/4" from top edge all the way around. Then, push elastic thru back section of casing only with a safety pin, attaching (sewing down) elastic at either side seam. Sew over lower casing openings (the holes that you threaded the elastic into). Now, it should look like this:
Next, attach the sequined trim to the front of top at top and sides only (not bottom of trim):
Your pillowcase halter top is now complete! And sew-easy to do! A closer look at the trim:
After it got all pressed by the iron:
And what it looks like on. I paired mine with a favorite jacket from Forever 21, and a black belt. (I hope to make a self-designed wider black fabric belt to wear with this instead...but you get the idea... It now can go easily from office to evening with the addition of a necklace, loss of the jacket and perhaps a stiletto.