To share your map without the left-side menu, you can use the URL in the Embed code.

Access the Embed Code

There are two methods to access it: 

1. In the top toolbar, click the "MENU" button.
    
2. Click on the "Get Embed" button.

1. Save your map.
    
2. Click on the "Widget / Embed" button.

Copy the URL

After accessing the Embed code, follow these steps:

1. Click on the provided Embed code to copy it to the clipboard.
   It will look similar to the following example:
   
   
    
2. Open a text editor, such as Notepad or any other document.
    
3. Paste the code into the text editor.
    
4. Remove everything outside of the URL, so you are left with something like this:
   
    
5. Share this link with others to allow them to view your map without the left-side menu.

Related:

Sharing and Presenting a Map - (E.g. Reddit post)

Embedding a Map - Blogger, Blog/Website, WordPress