Laravel unique slug generator in Model Class. Add this function in your model class.

slug.php

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class Post extends Model
{
    //...................................
    
    # verify and return custom slug string
    public function slugify($text)
    {
        # remove ? mark from string
        $slug = preg_replace('/\?/u', ' ', trim($text));
        $slug = preg_replace('/\s+/u', '-', trim($slug));

        # slug repeat check
        $latest = $this->whereRaw("slug REGEXP '^{$slug}(-[0-9]+)?$'")
                       ->latest('id')
                       ->value('slug');

        if($latest){
            $pieces = explode('-', $latest);
            $number = intval(end($pieces));
            $slug .= '-' . ($number + 1);
        }

        

        return $slug;
    }

}