how to make it so a button shows a GUI box

I’m trying to make a Inventory system on my game but when i looked at some basic codes from here all i can see are made in JS or they don’t work. Here’s my code so far:

using UnityEngine;
using System.Collections;

public class Inventory : MonoBehaviour {
	
	void OnGUI () {
		if (GUILayout.Button(Rect(10, 70, 100, 40), "Inventory") {
			GUILayout.Box(Rect(10, 10, 100, 60), "Inventory");
		}
	}
}

(GUI.Button(new Rect(10, 70, 100, 40) will return true only for one frame if the button get clicked. You need to keep that the button was clicked in a permanent variable like this:

using UnityEngine;
using System.Collections;

public class Inventory : MonoBehaviour {
		
	bool isButtonClicked = false;
		
	void OnGUI () {
		if (GUI.Button(new Rect(10, 70, 100, 40), "Inventory")) {
			isButtonClicked = !isButtonClicked;
		}

		if(isButtonClicked){
			GUI.Box(new Rect(10, 10, 100, 60), "Inventory");
		}
	}
}