Insert eloquent array with arrays

Hello, i have little issue, or problem with inserting data. So i have form with three fields that are going to one table, and that is working, but i have 4th field which is array, so its declared as name=member_id[]. Now first i insert in primary table, and then i need to insert all of those member_id[] in second table, its one to many, but i dont want to make model for that second table. So i want to make it plain with insert method. Now i made it like this.

      $group= Group::create([//stuff here]);
      foreach ($request->input('member_id') as $member) {
        DB::table('group_members')->insert(['member_id' => $member, 'group_id(fk)' => $group->id, 'custom'=>'0']);
      }

and that works. But i have problem, if there is lets say 15 of those members, then 15 queries are executed, i feel like that is not needed. So i found that i can make it like this

DB::table('group_members')->insert([
    ['member_id' => $member, 'group_id(fk)' => $group->id, 'custom'=>'0']//first,
    ['member_id' => $member, 'group_id(fk)' => $group->id, 'custom'=>'0']//second, etc...
]); 

and i hope that runs one query? So its better for resources. But i just cant manage to implement foreach like in my situation now, to make those arrays, and to place it in that insert. I tried to build string that looks like array, but that of course doesnt work. Is there any solution where it could be like

      $group= Group::create([//stuff here]);
      foreach ($request->input('member_id') as $member) {
        // make arrays here
      }

//and then

DB::table('group_members')->insert([
//place made arrays here
]); 

Thanks very much. Im out of ideas already :(