Spawning with LayerMake

I am trying to figure out how to Get my map generator to procedurally generate faster than it is. Here is what I have thus far... any solutions would be great.

using UnityEngine; using System.Collections;

public class BlockBuilder : MonoBehaviour { public string levelName; public GameObject groundSprite; public int numberOfGroundTilesToSpawn = 5; public int OffsetDistance = 2; public bool generateBorder = true;

 private int MaxRandomOptionRange = 12;
 private ArrayList GroundBlocksArray = new ArrayList();
 private Vector3 OffsetLocation = new Vector3(0f, 0f, 0f);

  
 void Start()
 {
     GroundBlocksArray.Add(gameObject);
     Vector3 SpawnPoint = transform.position;
     StartCoroutine(BuildBlocks(numberOfGroundTilesToSpawn, SpawnPoint));
     transform.name = levelName;
 }
 private IEnumerator BuildBlocks (int Quantity, Vector3 SpawnPoint) 
 {
     while( GroundBlocksArray.Count < Quantity )
     {
         yield return new Object();
         int randomnumber = Random.Range(1,MaxRandomOptionRange);
         int randomspawncount = Random.Range(1,1);
         switch (randomnumber)
         {
             case 1:
                 OffsetLocation = new Vector3(SpawnPoint.x + OffsetDistance, SpawnPoint.y, 0f);
                 SpawnCollisionCheck(OffsetLocation);
                 SpawnPoint = OffsetLocation;
                 break;
             case 2:
                 OffsetLocation = new Vector3(SpawnPoint.x, SpawnPoint.y + OffsetDistance, 0f);
                 SpawnCollisionCheck(OffsetLocation);
                 SpawnPoint = OffsetLocation;
                 break;
             case 3:
                 OffsetLocation = new Vector3(SpawnPoint.x, SpawnPoint.y - OffsetDistance, 0f);
                 SpawnCollisionCheck(OffsetLocation);
                 SpawnPoint = OffsetLocation;
                 break;
             case 4:
                 OffsetLocation = new Vector3(SpawnPoint.x - OffsetDistance, SpawnPoint.y, 0f);
                 SpawnCollisionCheck(OffsetLocation);
                 SpawnPoint = OffsetLocation;
                 break;
             case 5:
                 for (int i = 0; i < randomspawncount; i++)
                 {
                     OffsetLocation = new Vector3(SpawnPoint.x, SpawnPoint.y + OffsetDistance, 0f);
                     SpawnCollisionCheck(OffsetLocation);
                     SpawnPoint = OffsetLocation;
                 }
                 break;
             case 6:
                 for (int i = 0; i < randomspawncount; i++)
                 {
                     OffsetLocation = new Vector3(SpawnPoint.x, SpawnPoint.y - OffsetDistance, 0f);
                     SpawnCollisionCheck(OffsetLocation);
                     SpawnPoint = OffsetLocation;
                 }
                 break;
             case 7:
                 for (int i = 0; i < randomspawncount; i++)
                 {
                     OffsetLocation = new Vector3(SpawnPoint.x + OffsetDistance, SpawnPoint.y, 0f);
                     SpawnCollisionCheck(OffsetLocation);
                     SpawnPoint = OffsetLocation;
                 }
                 break;
             case 8:
                 for (int i = 0; i < randomspawncount; i++)
                 {
                     OffsetLocation = new Vector3(SpawnPoint.x - OffsetDistance, SpawnPoint.y, 0f);
                     SpawnCollisionCheck(OffsetLocation);
                     SpawnPoint = OffsetLocation;
                 }
                 break;
             case 9:
                 for (int i = 0; i < randomspawncount; i++)
                 {
                     OffsetLocation = new Vector3(SpawnPoint.x - OffsetDistance, SpawnPoint.y, 0f);
                     SpawnCollisionCheck(OffsetLocation);
                     SpawnPoint = OffsetLocation;
                 }
                 OffsetLocation = new Vector3(SpawnPoint.x, SpawnPoint.y - OffsetDistance, 0f);
                 SpawnCollisionCheck(OffsetLocation);
                 SpawnPoint = OffsetLocation;

                 for (int i = 0; i < randomspawncount; i++)
                 {
                     OffsetLocation = new Vector3(SpawnPoint.x + OffsetDistance, SpawnPoint.y, 0f);
                     SpawnCollisionCheck(OffsetLocation);
                     SpawnPoint = OffsetLocation;
                 }
                 break;
             case 10:
                 for (int i = 0; i < randomspawncount; i++)
                 {
                     OffsetLocation = new Vector3(SpawnPoint.x + OffsetDistance, SpawnPoint.y, 0f);
                     SpawnCollisionCheck(OffsetLocation);
                     SpawnPoint = OffsetLocation;
                 }
                 OffsetLocation = new Vector3(SpawnPoint.x, SpawnPoint.y + OffsetDistance, 0f);
                 SpawnCollisionCheck(OffsetLocation);
                 SpawnPoint = OffsetLocation;

                 for (int i = 0; i < randomspawncount; i++)
                 {
                     OffsetLocation = new Vector3(SpawnPoint.x - OffsetDistance, SpawnPoint.y, 0f);
                     SpawnCollisionCheck(OffsetLocation);
                     SpawnPoint = OffsetLocation;
                 }
                 break;
             case 11:
                 for (int i = 0; i < randomspawncount; i++)
                 {
                     OffsetLocation = new Vector3(SpawnPoint.x, SpawnPoint.y + OffsetDistance, 0f);
                     SpawnCollisionCheck(OffsetLocation);
                     SpawnPoint = OffsetLocation;
                 }
                 OffsetLocation = new Vector3(SpawnPoint.x - OffsetDistance, SpawnPoint.y, 0f);
                 SpawnCollisionCheck(OffsetLocation);
                 SpawnPoint = OffsetLocation;
                 for (int i = 0; i < randomspawncount; i++)
                 {
                     OffsetLocation = new Vector3(SpawnPoint.x, SpawnPoint.y - OffsetDistance, 0f);
                     SpawnCollisionCheck(OffsetLocation);
                     SpawnPoint = OffsetLocation;
                 }
                 break;
         }
         
     }

     if( generateBorder )
         GetComponent<BorderBuilder>().BuildBorderArray(GroundBlocksArray);

 }

 public bool SpawnCollisionCheck(Vector3 OffsetLocation)
 {
     var SpawnValid = true;
     foreach(GameObject b in GroundBlocksArray )
     {
         if( b.transform.position == OffsetLocation )
         {
             SpawnValid = false;
             return false;
         }
     }
     if( SpawnValid == true )
     {
         SpawnBlock( OffsetLocation );
         return true;
     }
     else
         return false;
 }

 public void SpawnBlock(Vector3 OffsetLocation)
 {
     GameObject groundTile = GameObject.Instantiate( groundSprite, OffsetLocation, Quaternion.identity) as GameObject;    
     GroundBlocksArray.Add( groundTile );
     groundTile.transform.position = OffsetLocation;
     groundTile.transform.parent = transform.FindChild("Ground");
 }

   

}