Take an old skirt, this works the best if the skirt has an wide waistband.

Put it on upside down. So the waistband is still on your waist, but the bottom is around your upper half.
Measure how wide you want your top to be.

Sew and cut of the fabric that is left on both sides.

If you like you top to be strapless, then your finished.
But.....

I wanted sleeves. So I took the fabric that I cut. It was shaped like a triangle. I cut de top edge and folded it in half.

so it looks like this.

Pin onto your top and if your satisfied sew it on.

You should and up with something like this.

The end result.

The back.

I am very pleased with the result.
I hope you like it too.