Custom post type should have below settings:

‘rewrite’ => false,
‘query_var’ => false,
‘publicly_queryable’ => false,
‘public’ => false

Explanation of each:

rewrite Triggers the handling of rewrites for this post type. To prevent rewrites, set to false.

query_var ‘false’ – Disables query_var key use. A post type cannot be loaded at /?{query_var}={single_post_slug}

publicly_queryable Whether queries can be performed on the front end as part of parse_request().

public ‘false’ – Post type is not intended to be used publicly and should generally be unavailable in wp-admin and on the front end unless explicitly planned for elsewhere.

Go to Permalinks Settings and without changing anything – save change. It will rebuild your “routing”.

Source: https://stackoverflow.com/questions/19747096/remove-url-structure-for-custom-post-type