How to collect the crafted item into inventory in unity2d

Question

Currently, I want to make a mini game where the player can craft item from very fundamental item to very advanced item (e.g. from a piece of wood then craft it into a spear). Basically it is some sort of Crafty by Brackeys but I would like to make my own version of Crafty!

I have been following the tutorial: https://www.youtube.com/watch?v=1fbd-yTcMgY&t=336s The crafting system is very simple to understand. I also finished a inventory system that can store the material but now I am facing a problem is that I cannot collect the crafted item from the Result Slot. Does anyone know code the coding in the video so that I able to collect the item from Result Slot into my inventory?

Code is posted as below. Thank you in advances

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;

public class CraftingManager : MonoBehaviour
{
private Item currentItem;
public Image customCursor;

public Slot[] craftingSlots;

public List<Item> itemList;
public string[] recipes;
public Item[] recipeResults;
public Slot resultSlot;

private void Update()
{
    if (Input.GetMouseButtonUp(0))
    {
        if(currentItem != null)
        {
            customCursor.gameObject.SetActive(false);
            Slot nearestSlot = null;
            float shortestDistance = float.MaxValue;

            foreach(Slot slot in craftingSlots)
            {
               float dist = Vector2.Distance(Input.mousePosition, slot.transform.position);

                if (dist < shortestDistance)
                {
                    shortestDistance = dist;
                    nearestSlot = slot;
                }
            }

            nearestSlot.gameObject.SetActive(true);
            nearestSlot.GetComponent<Image>().sprite = currentItem.GetComponent<Image>().sprite;
            nearestSlot.item = currentItem;
            itemList[nearestSlot.index] = currentItem;

            currentItem = null;

            CheckForCreatedRecipes();
        }
    }
}

public void OnClickSlot(Slot slot)
{
    slot.item = null;
    itemList[slot.index] = null;
    slot.gameObject.SetActive(false);
    CheckForCreatedRecipes();
}

public void OuMouseDownItem(Item item)
{
    if (currentItem == null)
    {
        currentItem = item;
        customCursor.gameObject.SetActive(true);
        customCursor.sprite = currentItem.GetComponent<Image>().sprite;
    }
}

void CheckForCreatedRecipes()
{
    resultSlot.gameObject.SetActive(false);
    resultSlot.item = null;

    string currentRecipeString = "";
    foreach(Item item in itemList){
        if(item != null)
        {
            currentRecipeString += item.itemName;
        }
        else
        {
            currentRecipeString += "null";
        }

    }

    for (int i = 0; i < recipes.Length; i++)
    {
        if(recipes[i] == currentRecipeString)
        {
            resultSlot.gameObject.SetActive(true);
            resultSlot.GetComponent<Image>().sprite = recipeResults[i].GetComponent<Image>().sprite;
            resultSlot.item = recipeResults[i];
        }
    }

}



}