I don't remember how I've gotten the idea - it was definitely someone else's idea, I'm just not this creative. Anyway, they turn out super cute and are crazy-easy to make! We went garage sale-ing Saturday and got some really cute adult tank tops for me to turn into skirts for our Princess.
I lay the tank out on the board and I use a straight edge and rolling cutter for a straight cut right under the under-arm seams.
Turn it inside out, fold an small edge down. I iron it so it's easier for me. Then sew the edge down leaving enough room to feed your elastic through. Make sure you don't sew it all the way around - you'll need a hole to put the safety pin and elastic in.
Then I take the elastic - I accidentally made this one too big w/o thinking... I would put the elastic around the Princess' waist and cut it 2+ inches too short, that way you have appropriate gather. Poke a safety pin through an end and feed it through.
Once you're at the end of the of the elastic, make a quick vertical stitch and back stitch so the elastic doesn't move. Finish feeding it through, do another vertical stitch and back stitch and sew up the rest of the fold.
Ta-Da! The Princess and her Butterfly skirt. :-)
My Princess is a 5/6 and Med-Lg women's tanks work best for her. She likes them as long as she can get them, so she wears them on the lowest part of her hips, as well.