Created an example for pouch.

Assets/Scenes/Testing Arena (Tony Edit).unity

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@@ -10774,6 +10899,7 @@ MonoBehaviour:
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   pickUpRange: {fileID: 1933067162}
   targetAttachment: {fileID: 0}
+  PlaceInContainerOfItemInSlot: {fileID: 0}
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@@ -27678,6 +27805,7 @@ MonoBehaviour:
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   targetAttachments:
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Assets/SimpleInventorySystem/Prefabs/Pickup.prefab

@@ -52,6 +52,7 @@ MonoBehaviour:
   itemUI: {fileID: 0}
   pickUpRange: {fileID: 41448510249244371}
   targetAttachment: {fileID: 0}
+  PlaceInContainerOfItemInSlot: {fileID: 0}
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   m_ObjectHideFlags: 0
@@ -63,7 +64,7 @@ SphereCollider:
   m_IsTrigger: 1
   m_Enabled: 1
   serializedVersion: 2
-  m_Radius: 0.25
+  m_Radius: 1
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 GameObject:

Assets/SimpleInventorySystem/Scripts/Inventory/PickUp.cs

@@ -19,6 +19,7 @@ namespace SimpleInventorySystem
         public PickUpRange pickUpRange;
         public bool HadPickedUp { private set; get; }
         [HideInInspector] public TargetAttachment targetAttachment;
+        public SlotUI PlaceInContainerOfItemInSlot;
 
         // Start is called before the first frame update
         void Start()
@@ -116,6 +117,35 @@ namespace SimpleInventorySystem
                         }
                     }
                 }
+
+                // assume there is no tsp, then try to drop in most available backpack slot
+                if (PlaceInContainerOfItemInSlot != null)
+                {
+                    if (PlaceInContainerOfItemInSlot.GetItemUI() != null && PlaceInContainerOfItemInSlot.GetItemUI().container != null)
+                    {
+                        GridUI grid = PlaceInContainerOfItemInSlot.GetItemUI().container.GetComponent<GridUI>();
+                        if (grid != null)
+                        {
+                            if (grid.DropItemOnGrid(itemUI.gameObject))
+                            {
+                                Debug.Log("PickUp: Placed in grid.");
+                                HadPickedUp = true;
+
+                                // TODO: Handle changing transform here
+                                //ItemGameObject.GetComponent<>;
+
+                                if (InventorySystem.instance.player.AttachItemGameObject(ItemGameObject, itemUI.ItemTag, itemUI))
+                                {
+                                    pickUpCollider.enabled = false;
+                                    pickUpRange.GetComponent<Collider>().enabled = false;
+                                }
+                                return;
+                            }
+                        }
+                    }
+                }
+
+                Debug.Log("Could not pick up");
             }
         }
 

Assets/SimpleInventorySystem/Scripts/Inventory/Player_IS.cs

@@ -51,7 +51,7 @@ namespace SimpleInventorySystem
         {
             if(storedPickUp != null && pickUpsInRange.Contains(storedPickUp))
             {
-                Debug.Log("Picking up");
+                Debug.Log("Picking up" + storedPickUp.name);
                 storedPickUp.PickUpHandler();
             }
         }

Assets/SimpleInventorySystem/Scripts/Inventory/TargetAttachment.cs

@@ -17,7 +17,7 @@ namespace SimpleInventorySystem
 
         public bool AttachItemGameObject(GameObject go, ItemTags targetItemTag, PickUp pickUp)
         {
-            if (itemTag == targetItemTag)
+            if (itemTag == targetItemTag || itemTag == ItemTags.Any)
             {
                 itemGameObject = go;
 
@@ -48,6 +48,10 @@ namespace SimpleInventorySystem
 
         public void DetachItemGameObject(GameObject go)
         {
+            if (hideGameObject)
+            {
+                itemGameObject.SetActive(true);
+            }
             itemGameObject = null;
             // TODO: Most likely, implement drop here.
             go.transform.SetParent(null);

Assets/SimpleInventorySystem/Scripts/UI/GridUI.cs

@@ -29,6 +29,7 @@ namespace SimpleInventorySystem
         public GameObject[] testItems;
         private Size cellSize;
         public Size CellSize { get { return cellSize; } }
+        private Vector2 nextAvailableCellCoords;
 
         private void Awake()
         {
@@ -109,7 +110,7 @@ namespace SimpleInventorySystem
                     int i = 0;
                     int x = 0, y = 0;
                     int lootCount = 1;
-                    foreach (GameObject testItemUI in testItems)
+                    foreach (GameObject testItem in testItems)
                     {
                         bool dropped = false;
                         GameObject item = null;
@@ -120,14 +121,13 @@ namespace SimpleInventorySystem
                                 x = i % gridSize.Width;
                                 y = i / gridSize.Width;
 
-                                item = Instantiate(testItemUI);
+                                item = Instantiate(testItem);
                                 item.name = item.name + " " + lootCount;
                                 dropped = cells[y, x].slot.DropOntoSlot(item);
 
                                 if (!dropped)
                                 {
                                     Destroy(item);
-
                                 }
                                 else
                                 {
@@ -146,11 +146,58 @@ namespace SimpleInventorySystem
                             Debug.LogWarning("Could not add all test items");
                             break;
                         }
+
+                        // TODO: Make sure this works as expected
+                        nextAvailableCellCoords = new Vector2(i % gridSize.Width, i / gridSize.Width);
                     }
                 }
             }
         }
 
+        public bool DropItemOnGrid(GameObject item)
+        {
+            if (item != null)
+            {
+                int i = 0;
+                int x = (int)nextAvailableCellCoords.x, y = (int)nextAvailableCellCoords.y;
+                bool dropped = false;
+                try
+                {
+                    do
+                    {
+                        x = i % gridSize.Width;
+                        y = i / gridSize.Width;
+
+                        dropped = cells[y, x].slot.DropOntoSlot(item);
+
+                        if (!dropped)
+                        {
+                        }
+                        else
+                        {
+                            item.transform.localScale = new Vector3(1, 1, 1);
+                            // TODO: Make sure this works as expected
+                            nextAvailableCellCoords = new Vector2(i % gridSize.Width, i / gridSize.Width);
+                            return true;
+                        }
+                        i++;
+                    } while (!dropped); // TODO: perhaps add a check to make sure i has not exceeded the total number of slots
+                }
+                catch (IndexOutOfRangeException err)
+                {
+                    Debug.LogWarning("GridUI: " + x + ", " + y);
+                    return false;
+                }
+
+                return false;
+            }
+            else
+            {
+                Debug.LogWarning("GridUI: Could not add item to grid.");
+                return false;
+            }
+        }
+
         // Start is called before the first frame update
         void Start()
         {