math_cms/app/Filament/Resources/TextbookResource/Pages/CreateTextbook.php

<?php

namespace App\Filament\Resources\TextbookResource\Pages;

use App\Filament\Resources\TextbookResource;
use Filament\Resources\Pages\CreateRecord;

class CreateTextbook extends CreateRecord
{
    protected static string $resource = TextbookResource::class;
}