I modified mine a little bit to make it a little more fancy for Easter (mine is more of a pencil skirt) but you can easily make a more casual version. I hope this makes sense...I wish I was able to take more pictures but I was frantically sewing and hanging out with Rilo in between sewing. Here's how to make it:
2-3 yards fabric
1 t-shirt (this would be great if you shrunk a shirt or got a stain on it)
scissors or rotary cutter
First you need to measure around your natural waist. Then from your waist to where you want the skirt to hit. I went a little below the knee because I was going for a pencil skirt feel.
Now take your waist measurement and add 1". Cut a strip of fabric 3.5" by whatever your waist measurement is+1. This will be the waistband.
You're going to cut out 2 pieces for your skirt. Cut your skirt to your desired length. The width will be your waist measurement plus a few inches. I like to err on the side of larger than I will need it so I can better tailor it later. I added 4 inches...I know, like I said I like to make sure I have something extra to work with!
With right sides together, sew the 2 shorter ends of your waistband.
Again with right sides together, sew the side seams of your skirt.
Now you're going to attach the skirt to the waistband. To do this I first matched up the side seams and pinned, and then kept pinning the midpoint between 2 pins, until it was pinned all the way around.
Sew a 1/4" seam. Then sew a zig-zag stitch close to the edge so your fabric doesn't fray. At this point, I suggest trying on your skirt and tailoring it to fit. To do this, determine how much you need to take off each side (if any). In my case, about 1.5". Turn your skirt back inside out, so your right sides are touching again, and measure in 1.5" on each side and mark with pins. Then sew a new seam parallel to your old seam. Cut of your excess.
Then you need to hem the bottom (fold over 1/4" and press, then fold another 1/2", press and sew).
Try on your t-shirt and determine where you want the waistband to meet the shirt and make a mark with a fabric pen. Then cut your shirt.
All that's left is attaching your t-shirt to the waistband. You do this in the same way you pinned the skirt to the waistband. Sew your 1/4" seam and then zig-zag stitch again.
Voila! You have a t-shirt dress! And here is a terrible picture of the final result...Adam didn't get home until late so we lost all the natural light! (Also, could I be any whiter?)