Creating room construction 2d builder

Hi,

I want to make a game where the user selects a wall and can then place that on the map. Currently the player can place one wall and then the next and the next. Not the quickest and easiest way.I want him to be able to draw a whole line or a room. at once with simply dragging the mouse.

The problems i'm facing are that the walls look cool, but they don't turn automatically and don't merge well together. How is this even done when you have a complete room building option at once?

Any suggestion on how to proceed? I have been trying to find information about 2d sprites and using the sprite editor to help me with coding

Here is the code I have for placing a wall:

 void Update () {
     if (currentBuilding != null && keepPlacing) 
     {
         Vector3 m = Input.mousePosition;
         Vector3 p = camera.ScreenToWorldPoint (m);
         currentBuilding.position = new Vector3 (p.x, p.y, 0);

         if (Input.GetMouseButton (0) && GUIUtility.hotControl == 0) 
         {
             BuildingsChosen(activeBuilding);
         }

         if (Input.GetMouseButtonDown (1)) 
         {
             Destroy (activeBuilding);
             hasPlaced = true;
             keepPlacing = false;
         }

     }
 }

with currentbuilding being assigned by clicking the corresponding button. Right now I want to focus on making the sprites look good together and have a smooth overflow, and not focus on the grid placement so much. That one will be easier (I think).