The shape will come back after dunk, pat dry with towel, and carefully stuffed with towels to dry. Do not over stuff otherwise will stretch the leather.
I usually fold a soft hand towel to the same width as the interior bottom. Lay the bag flat and line the hand towel along the bottom , with extra length bend and line along the sides of bag. Then fold more towels to stuff the bag to desired shape. You can gently pat the bottom or each sides to adjust the shape till you are happy with it. Don't forget to Condition the leather after 8 to 24 hrs while the bag is still damp, depends on how fast the leather dries in your home environment. Usually after a day or two, you can remove the towels, and the bag will retain the shape while drying.