Sample-page in path of permalinks won't go away

I can’t get /sample-page/ out the path of all of my permalinks. Whenever I select Custom Structure on the Permalinks page, it just moves the selection back to the Post name (/sample-post) option. I assume that Post name is what I want, but I want the real path, without /sample-post/ inserted into it…

I read in another post that removing the parent fixes this, but the menu structure is determined by this, so how can I do this without breaking the menu structure?

Thanks for any help.