Note that while the trophy description lists to fill the stomach stock completely, it’s actually a little misleading. You just need to find enough stomach stones to open all of the spaces in the stomach stock and it’ll unlock. If you’re aiming for 100% map completion and fully explore each area, by the time you get to the pillar before the Chapter 11, Part 2 boss you should have found all of the stomach stones in the one playthrough. Just be sure to open every black chest in the game as you fully explore the maps and you should come across this easily.