I did prototypes with cardboard initially, which helped me identify and solve some potential issues. I solved some mistakes I made in the finger joint parts, and I tried several ways to support the surface in the bottom box during the prototype.
Finally, I decided to do more finger joints as the support, which worked fine after several testing attempts.
When I was done with the prototype, I chose birchwood as the material. I like the burned edge of birchwood, and those brown edges make finger-jointed boxes pretty.
And then, I put my Arduino inside the box. As the video shows, the speaker makes noises when I get my phone out of the box.
The only problem is that the phone larger than mine cannot fit in a box of sizes smaller than 7 inches, so many phones cannot use this box. In the future, I might come up with a larger container. Next time, I might choose acrylic as the material and make other containers or installations. Acrylic boxes or structures get even more beautiful when there is some light inside. I would like to develop some interesting ideas and add some led lights inside.