This is the same area where you can find the Arboretum Armory crafting station. The set you can craft here is called Redistributor. It offers additional Health, Stamina and Magicka for wearing 2, 3 and 4 items. When you have all 5 items, a nearby ally will be healed as you heal yourself while at full health.
The exact location you should head to is in the northwestern corner, in the water. There is a small pond, close to the central wall. The pile of rancid flesh doesn’t seem like something worth searching for. It is a rather small pile and hard to notice. This is due to the fact that this small pond is a bit lower than the rest of the area. The shard’s glow is hard to spot from the distance. It only started to glow as I was coming close to the spot. If you’ve looked at the map, you’ll find it easily. It is the lonely corner, with no enemies nearby.
Sand Kingdom Moons - Super Mario Odyssey Power Moons