Remove base slug of Custom Post Types and change the permalink structure of Custom Post Types.

Add rewrite rules for custom post type so that the urls for them are in the same way as normal posts: http://siteurl/%custom_post_type_title%/.

This simple and small plugin removes the /blog/-Slug from your WordPress posts in the main blog of your MultiSite installation

Add rewrite rules for custom post type so that the urls for them are in the same way as normal posts: http://siteurl/%custom_post_type_title%/.