How to host the Primary Domain from a subfolder (.htaccess)

RewriteEngine on 

# Change example.com to be your main domain. 

RewriteCond %{HTTP_HOST} ^(www.)?example.com$ 
# Change 'subdirectory' to be the directory you will use for your main domain. 
RewriteCond %{REQUEST_URI} !^/subdirectory/ 
# Don't change the following two lines. 
RewriteCond %{REQUEST_FILENAME} !-f 
RewriteCond %{REQUEST_FILENAME} !-d 


# Change 'subdirectory' to be the directory you will use for your main domain. 
RewriteRule ^(.*)$ /subdirectory/$1 

# Change example.com to be your main domain again. 
# Change 'subdirectory' to be the directory you will use for your main domain 
# followed by / then the main file for your site, index.php, index.html, etc. 
RewriteCond %{HTTP_HOST} ^(www.)?example.com$ 
RewriteRule ^(/)?$ subdirectory/index.html [L]