I was storing my flaps upright when I spotted a pesky crease forming toward the bottom of the front (lambskin). This was a bag I only carried less than a handful of times. So now I lay them flat.
Good to know because i also store my bag upright.
I heard laying them flat, mainly lamb, causes the quilts to flatten over time? Seems like there's no perfect way? I was always told to store them upright with no pressure to be placed on the quilts.