I saw this idea a LONG time ago, but didn’t try it out until I was going through some craft supplies in the basement. I love it because it was SO EASY and only involves saving small boxes or packaging from actual picture frames.
We simply used a glue stick to attach his masterpieces to the cardboard box / frame. The blue picture was made using his fingerprints and the larger one is his interpretation of our garage.
Here are the finished products:

Cute, huh?! I think it looks more official than just hanging it on the fridge. And I encouraged him to draw around the blue picture with other markers for another “frame” in the frame. There are a lot of things you could do with this project if you so choose.
Have a great day & happy crafting!