Originally Posted By: MostlyHarmless
One scenario that is important for me is melting snow. Adding snow to a narrow slot is painful and tedious. For this purpose I suggest that the flask opening has a shallow "U"-shape at one side (about 1-1.5 inch deep). This wider opening should make stuffing snow in there much easier, and you could also use the hip flask to scoop up snow directly.

It seems to me, that will just lower the volume of the flask. You should be able to scoop the snow perfectly as is, with flat opening. AFAIK, air easily pass through the not compacted snow (correct me if I'm wrong), so all you need is to drive the flask into a clean patch of snow, mouth first, and it will be efficiently filled.