💡 Detailed Explanation
The correct order is 「よく 相談した 上で 改めて」. The grammar point is 「～た上で」, which means 'after doing X, then do Y', emphasizing a deliberate, sequential process. The full sentence is 「この件につきましては、関係者とよく相談した上で、改めて決定したいと思います。」. The word that goes in the star (★) is the third one in the sequence, which is 「上で」.