I found a large 20x30 poster frame at Walmart for about $12. I then removed everything so I just had the frame. I bought a foam board there for $3. They come in 20x30 size so this is the reason I got the frame in that size. I didn't want to do any cutting (I can't cut a straight line to save my life).
I bought a few cheap decorations for Halloween and Thanksgiving. The dollar store has a lot of little things that are fun for this project. But, you can always go to Hobby Lobby, Walmart, or other craft stores.
I then took my foam board and hot glue gun. I didn't even lay things out before I started. I just began to glue until I had all my items glued on. Once I got it all glued, I put it in my frame. The foam board popped right in and the latches on the back of the frame held it tight.
I did the Halloween and Thanksgiving/Autumn board to show how easy it is. You literally use the same frame and just swap out the Holiday. This is great for any Holiday. Christmas, Easter, 4th of July, etc.
It is so easy because the foam boards are so cheap and you can store them year after year and use your same frame to showcase the Holiday in your own way.
I have a spot on my wall where that picture hangs year round and I change out the theme.
People that come over love it and ask where I got the "Art Piece". I usually just lie and tell them it is an original and they could never afford it *wink*.