[quote=@Conibear]
Ah but what if the bag itself was beyond the standard Euclidean Geometry and in fact functioned as a non-Euclidean device? And the bag is in fact, not three dimensional like everything else, but was in fact a four dimensional object. And the bag itself is the only real three dimensional object is the bag itself, while the inside is a four dimensional space which hosts the actual stuff.

Imagine the world as 2D existence on a piece of paper, with every citizen as a two dimensional stick figure, and the bag is featured as another drawing. The could move items around the bag, but when placing a thing in it is now off the page of reality yet still within the 2D bag.

Or something like that. Or Hell, it could just be magic and I move my dude slightly more towards magic inclined. Who knows.
[/quote]

A Bag of Holding that operates more on pseudoscience would probably be something like "the rim of the bag is a [i]matter condenser[/i] that harmlessly compresses anything that passes by it, and reverses the process when something is pulled through it in the opposite direction."

You could also go for something with pocket dimensions and the bag is actually a portal that activates whenever the bag is opened.