Hey how can I spawn a platform after the previous one.

Hey, I want to spawn a random platform every time, but attach to the previous platform, Could some please look at the my code and help me, The platform prefabs are all different sizes. The spawning part is working but I am having trouble attaching one platform to the other perfectly. I have attached this code to the starting platform. Any help would be great. Thanks.

using UnityEngine; using System.Collections;

public class Spawn : MonoBehaviour {

 public float spawnSpeed;
 
 public GameObject[] platformPrefabArray;
 
 private GameObject lastCreatedPlatform;

 private Vector3 lastPlatformPosition;
 
 public Vector3 offset;
 
 void Awake()
 {
     spawnSpeed = 1f;
     lastPlatformPosition = new Vector3 (0, 0, 1);
     offset = new Vector3 (0, 0, 25);
 }
         
         void Start()
         {
         CreatePlatform() 
         }
         


         void CreatePlatform()
 {
     lastCreatedPlatform = (GameObject)Instantiate(platformPrefabArray  [Random.Range (0, platformPrefabArray.GetLength (0))], lastPlatformPosition + offset, Quaternion.identity);
     lastPlatformPosition = lastCreatedPlatform.transform.position;
         
 }
 

}