I found your phrasing interesting. If you want the binding to show 1/4" on the top, then all you have to do is make sure you sew it on 1/4" from the raw edge. Once you fold it to the back, you'll only have 1/4" showing on the front. It won't really matter how wide you originally cut it.
If you want it to show 1/4" on both the front
and the back, that's a different story.
