that's it! now you should have one big donut. laying flat, the inner circle will measure 36", but when you open it up and stretch it out a bit, it should be closer to the 40" measurement that we want.
measure it just to make sure, and if you need to make it a little bigger, go ahead. just take a sliver off that inner circle to make it a little bigger. go slow, because like I said before, too big is harder to fix than too small.
attach it to your dress, skirt, or waistband, and you're done.
NOTE: depending on the size of your donut and the length you want your skirt to be, you might need to cut your donut into sections.
you might need to make it in 2 sections (so you'll have 2 half donuts, which you can then sew together) or 4 sections.
if you want to see it in action, look at the examples. the 2nd skirt (the stripey Misfits one) is cut into 4 sections. you can see the 2 front panels in the photo.
keep reading for variations on the circle skirt...