Do you want the legs for function or looks? We use ours on their sides without legs. If I were going to add legs, I'd probably go for prettypegs.se/, but you'd have to drill holes to use them.
I'd like to raise it up so I can store some low baskets underneath. But I also like how it looks more like a piece of living room furniture (which is where we will place it).
I've done this without legs, it looks good. If you want to do legs, keep in mind that it's not solid wood, it's just cardboard inside of a pretty exterior. You won't be able to actually screw anything in.