FavoritePodcast::query()->insertUsing(
    ['id', 'created_at', 'user_id'],
    Podcast::query()
        ->where('category_id', 123)
        ->select(['id', DB::raw('? as created_at'), DB::raw('? as user_id')])
        ->addBindings(
            [now(), $user->id],
            'select' // this will now give me a static analysis warning if I input something bogus, and it's much easier to discover what the acceptable values are
        )
);