Here's a link for you:
Here's one shadow box idea, hope it helps. https://www.hometalk.com/10049142/how-to-made-a-shadow-box
Check youtube videos
All good answers above. If you don't have a miter saw that can cut angles and bevels, and you end up doing butt joints, make the joints so they don't show end grain on the sides of your box.
This might help: https://www.hometalk.com/33920125/diy-shadowbox-snowflake-shaker-artwork