ldc-doux/database/seeders/SlidersSeeder.php

<?php

namespace Database\Seeders;

use App\Models\Slide;
use App\Models\Slider;
use Illuminate\Database\Seeder;

class SlidersSeeder extends Seeder
{
    /**
     * Run the database seeds.
     *
     * @return void
     */
    public function run()
    {
        Slider::factory(1)->create()
            ->each(function (Slider $slider): void {

                $i = 0;
                Slide::factory(3)->make()
                    ->each(function (Slide $slide) use ($slider, &$i): void {
                        $slide->order = $i++;
                        $slide->slider()->associate($slider);
                        $slide->save();
                    });
            });
    }
}