https://i.imgur.com/7ZzQT1P.png
Found all 12 gift boxes fairly quickly, dragging them into my inventory, along with the items. After I found the 12th box and arranged everything in a photo, I then realized that I was missing the cube! It took me a while to find it because, of course, I had to search the entire house again, and that thing is tiny!
If you haven't completed this challenge yet, a word to the wise -- make sure you have not only the gift box, but the item, too! LOL. I was having too much fun searching to notice one was missing.
Good luck, everyone!