This populator places object that should be placed in a uniform, random distribution, unlike the Environment populator which uses a noise map.

Detail_Populator.cs

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

public class Detail_Populator : MonoBehaviour
{
    
    //These two variables control how far the objects could potentially be placed. 
	//Ex. If these two variables were set to 20, the the farthest an object could be placed is at (20,0,20)
    public float EndRangeX;
    public float EndRangeY;
    
	//Because this populator doesn't use a noise map to spawn objects, we need to specify how many objects the populator has to spawn
	public int NumberofObjectsToSpawn;
    
	//This is the list of prefab/gameobjects the populator could spawn
    public List<GameObject> spawnGameObjects = new List<GameObject>();
    
	//We make a list to manipulate the gameobjects we have spawned. We make sure to hide it in the editor because there's no point in showing it
    [HideInInspector]
    public List<GameObject> spawnedGameObjects = new List<GameObject>();


	//Similar to the environment populator, we define a function that gives us a list of Vector3s positions
    public  List<Vector3> GetSpawnVectors(){
		
		//we make a list to add on Vector3s for
        List<Vector3> NewList = new List<Vector3>();
		
		//We make a loop that will iterate depending on how many objects we want to spawn
        for(int i=0; i < NumberofObjectsToSpawn; i++){
            
			//We create a new vector with the x and z components having a random number between 0 and the preivously specified upper bounds
			//We then add that Vector3 to the list 
			NewList.Add(new Vector3(Random.Range(0, EndRangeX), 0, Random.Range(0, EndRangeY)));
        }
		//We make the function give that list of Vector3
        return (NewList);
        
    }

	//This is the function that actually spawns our gameobjects
    public void Spawn_Objects(){
        //We create a vector3 list and set it to GetSpawnVectors() which gives us the random positions
		List<Vector3> SpawnVectors = GetSpawnVectors();

		//We go through that list, setting the Vector3 we're on as x 
        foreach (Vector3 x in SpawnVectors){
			
			//Similar to before, we create a gameobject and set it to a copied randomly selected object from that list, and then add it to a list.
            GameObject y = Instantiate(spawnGameObjects[Random.Range(0, spawnGameObjects.Count)], x, Quaternion.Euler(0, Random.Range(0,360), 0)) as GameObject;
            spawnedGameObjects.Add(y);
        }

    }

    public void Destroy_Objects(){
        foreach(GameObject x in spawnedGameObjects){
            DestroyImmediate(x);
        }
    }    

  
}