html form post in laravel 5.5.1 cant get the right routes

controller:

namespace App\Http\Controllers;

use Illuminate\Http\Request;

class SellauthController extends Controller {

protected function validator(array $data)
{
     return Validator::make($data, [
        'storename' => 'required|string|max:255',
        'city3' => 'required|string|min:5|max:100',
        'storelocation' => 'required|string|max:255',
        'pannumber' => 'numeric',
        'vatnumber' => 'numeric',
        'productcat' => 'required|string|max:255',
     ]);
}
protected function create(array $data)
{
    $userid = (!Auth::guest()) ? Auth::user()->id : null ;
    return Sellauths::create([
        'userid' => $userid,
        'storename' => $data['store-name'],
        'storelocation' => $data['city3'].$data['store-location'],
        'pannumber' => $data['store-pan'],
        'vatnumber' =>  $data['store-vat'],
        'productcat' => $data['store-product-types'],
        'active' => 0,
    ]);
    return User::update([
        'usercat' => 'sells',
    ]);
}

}

view / form <form class = "seller-reg-form" action="" method="post"> <h3 class = "in-page-title" > Register as a seller </h3> : : </form>

model:

namespace App;

use Illuminate\Database\Eloquent\Model;

class sellauth extends Model { use Notifiable;

    protected $fillable = [
        'userid','storename', 'storelocation', 'pannumber', 'vatnumber', 'productcat', 'usercat', 'blocksell', 'active'
    ];

}

via Chebli Mohamed