setBlockIdAt random blocks

Hi, I want to make random blocks like in the first picture, but I put random blocks in the chunks, ie 1 chunk is equal to one ID.

My code:

PHP:

          $cover = array(1, 13, 4, 1, 3);
        $this->setGroundCover([
            Block::get($cover[array_rand($cover)], 0),
            Block::get($cover[array_rand($cover)], 0),
            Block::get($cover[array_rand($cover)], 0),
            Block::get(1, 0),
            Block::get(1, 0),
            Block::get(1, 0)
        ]);