You can make it for sale at a base thathas only one pad at the ship dealer (for example, Pittsburgh). You might have to try different bases, for you can't really control which ship FL places on that pad.

Well, if you want to hide it, one option is to sink it into the ground. To do this, you'll need to be able to edit the hardpoints of the Osiris, meaning you'll want something that can read .cmp files (or you can just download the hardpoint editor that was posted here a little while back, it will work nicely for this). The hardpoint you'll want to alter is HPMount, which is what the game refers to when deciding where to place the ship when it's hovering over the landing pad (the HPMount of the default Osiris is about halfway down the bow, if that helps). So, if you move this hardpoint up very far vertically, the game will place the ship quite a ways below ground, and thus well out of sight.