Each custom post type and taxonomy has its own permalink structure (aka rewrite slug). Unfortunately, WordPress does not enable you to delete the rewrite slugs by default. This brief tutorial will teach you how to quickly delete permalink bases using Permalink Manager.
In general, you may use Permalink Manager to not only delete permalink bases, but also rename them or create whole new permalink structures. You may, for example, apply the same permalink base for multiple post types & taxonomies.
How to remove the slug (eg. portfolio-item) from the permalinks?
Fastest method: Bulk edit the custom permalinks
The most convenient and time-saving method is to modify multiple permalinks simultaneously. Indeed, it should take no more than a few minutes, and the entire process can be completed in three simple steps.
To begin, navigate to the section “Tools -> Permalink Manager -> Permastructures” section. Second, as illustrated below, you should remove the slugs for the post types and taxonomies you have chosen:
From now on, new permalinks will automatically delete the slugs. To complete this task, please regenerate the permalinks of the posts and keywords you just edited.
If you did not add any posts or terms earlier, you may skip this step. Please go to “Tools -> Regenerate/reset” section in Permalink Manager admin panel to reset the custom permalinks.
Alternative method: Edit the custom permalinks manually
It is also possible to remove the slugs from each of custom permalinks manually. At the same time, you can also fully customize the individual permalink any way you like.