If your WordPress site has a custom permalink structure but you don't want that default base slug for the taxonomy pages then use this code snippet to remove it.
/* Advanced Scripts Method to Add This Snippet */
add_filter( 'register_taxonomy_args', function( $args, $taxonomy )
{
if( 'category' === $taxonomy && is_array( $args ) )
$args['rewrite']['with_front'] = false;
return $args;
}, 99, 2 );