My index.html page is inside build folder and htaccess file is at public_html folder.

Before adding FallbackResource ./index.html it showing 403 error and after adding those lines throw an error code 500.

Can you help me on this?

<IfModule mod_rewrite.c>

RewriteEngine On

RewriteBase /

RewriteRule ^index\.html$ - [L]

RewriteCond %{REQUEST_FILENAME} !-f

RewriteCond %{REQUEST_FILENAME} !-d

RewriteCond %{REQUEST_FILENAME} !-l

RewriteRule . /index.html [L]

</IfModule>