How can I use bed skirts to upholster?

https://www.pinterest.com/explore/upholstered-bed-frame/

Yes you can, especially if your bed skirt material has weight. If it's the thin, sheet like material, it'll do but not look quite as nice.

I'd wrap and staple a thick layer of batting on first. Should be an easy project.

Thank you. What is the best foam or wood to use. That is easy to cut?. I do t have a circular saw.

The boards can definitely be cut with a circular saw. How are you attaching to the bed?

Use pine called 1 " they are actually 3/4" . Or plywood. Cut boards or plywood the desired width, ie almost the full space between frame and floor and the correct length. If you have a wood frame figure out how you want to attach. If you have a metal frame you may have to attached the panels with L brackets or similar from the rear after upholstering. Use batting OR several thicknesses of an old blanket to pad the board. Smooth batting over boards wrapping around the edges and stapling from the back. Then stretch skirt over batting again wrapping to the back and staple. You will need a construction stapler.

If you store treasures under the bed. I think the upholstered boards would prevent this. Also you would need to recess the boards for toe space.

I have skirts that do not have gathers, just straight fabric. I like them. Not girly and I can get to my crafts stored under the bed. If your existing skirt has gathers, just take it apart remove the gathers and resew into a smooth skirt cutting excess material off at the ends.