MS, the distance from the TV screen isn't the relevant factor. The most common suggestion is that the speakers should be separated by about the same distance as your listening spot is from them.
No, they don't necessarily have to be placed on stands if they're at the correct height, but if you place them on something else, they shouldn't be recessed into the supporting surface. For example, if they were placed on a shelf, the front edge of the speaker should extend a fraction of an inch forward of the shelf edge, to minimize diffractions and reflections from the shelf surface.
