All my kids moved out and I've taken over the boys bedroom with fabric (quilting and garment sewing)
We live in a 1915 Craftsman, and the room has carpeting that will not be removed, so the floors are uneven.
I bought some metal shelves from Home Depot, there are 4 shelves, each 2' x 3 ', 5 units.
My husband attached each shelving unit to the wall with zip ties that hook to an eye bolt screwed into the studs of the wall. No matter how uneven I make them, those shelves are not falling!