How to only use created_at in Laravel

Eloquent does not provide such functionality out of the box, but you can create it on your own using the creating event callback:

class User extends Eloquent {

    public $timestamps = false;

    public static function boot()
    {
        parent::boot();

        static::creating(function ($model) {
            $model->created_at = $model->freshTimestamp();
        });
    }

}