I don't really try to hide em anymore, unopened packs are mostly stored under the bed, with loose ones in a drawer. What I have used in the past however is an old armchair I have in my room from when we replaced furniture downstairs.
The chair itself under the cushion had a piece of fabric that had ripped off exposing the springs underneath, I found a piece of wooden board (MDF) that firs perfectly over them that the cushion now sits on. I tipped the chair onto it's back and cut off the fabric lining the base so that I can get into the inside of the chair under the springs.
Now I can tip the chair back a little, slide a pack or two of nappies underneath and lower the chair back down over them, perfectly hidden and if I need one I can just ligt the cushion and wooden board and pull one out of the pack through the springs.