Use loading scene to prepare game level ?

what I'm trying to do is load my "loading scene" when my "level scene" is preparing. But i can't do it. can anyone help me with this ?

 // Update is called once per frame
 public void play_game_button() {
     
         StartCoroutine(lev());
     
 }

 IEnumerator lev (){
     SceneManager.LoadScene("loading_scene");
     AsyncOperation asx = SceneManager.LoadSceneAsync("level02",LoadSceneMode.Single);
     yield return null;
     Debug.Log(asx.progress);
     if(asx.isDone){
         // remove loading_scene
     }
     Debug.Log("Done");
     
 }

there is another unprofessional way. I did not try it yet but if i did not get a answer for this i will try it. which is use canvas in the "level scene" as "Waiting scene". when level is full loaded this canvas will disappear.