What can I make using 40 pieces of wood?

Custom Wall art. If you choose to paint some pieces, like in the example photos, then coordinate with your existing drapes, upholstery, carpet & wall paint.

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There are quite a few ideas here!

https://www.familyhandyman.com/woodworking/surprisingly-simple-woodworking-projects-for-beginners/

How about a wall plaque with the wood placed in a herringbone pattern. You can stain different colors if you want to or all the same. Then frame. I've seen something like that in Hobby Lobby.

If you need 1 or would like to replace yours, a backsplash would a great idea.

Some ideas from other Hometalkers

https://www.hometalk.com/search/posts?filter=scrap%20wood%20ideas

You could make cutting boards or bandsaw boxes.

Here are some ideas: https://www.youtube.com/watch?v=PNAXFD8I4ns

Hello! It might be fun to make signs. That is very popular item right now. Particularly if you have a vinyl cutter. They also have memory marker - signs mounted on rope that indicate special places you’ve traveled or family moments. The one we were gifted has these locations with the actual milage from our homes location.

Can you glue or nail them together as the background of a sign like here? https://www.hometalk.com/39442890/rustic-wood-home-sign-with-a-eucalyptus-wreath

Here is a wooden vase holder I made with wood. https://lifeonsummerhill.com/farmhouse-flower-vase-diy/

DIY shadow boxes if you cut it down a bit. Maybe help frame windows, too?

The possibilities are endless! Photo frames, plant boxes etc.