This project is very easy but here are some steps you'll have to follow.

Step 1: After having all the parts cut, place it in a table to have a better view to attach them properly.

Step 2: Glue the small circle that its inside the number circle to the plain circle(back part of the ornament)

Step 3: After these parts are glued, you will place the number circle around the small circle you previously had glued.

Step 4: Then you will put some glue on the small circle to attach the top of the ornament, the one that's engraved with Hagrid pulling the tree. So the number circle will be free to roll.

Step 5: After checking that the numbers are moving smoothly, you can color the Christmas sign and glue it and  you're done.

step 6: Enjoy your Christmas countdown ornament. :D