Here I'm gonna show you the steps I followed to create an advent calendar shaped as a Christmas Tree, which can be hanged on a wall and contain sachets for each different day.

Step 1: Material

3 rectangular plastic containers of different sizes
1 circular plastic container
1 red ribbon
1 rigid paper (as rigid as possible)
1 green veiled paper
1 pencil
1 pair of scissors
1 double sided cellotape
1 long carton roll
25 christmas napkins
25 cookies/sweets/surprises/notes

The rectangular plastic containers I used, were containing, respectively, fruit, tomatoes and basil when I bought them from the supermarket (see image).

The circular plastic container I used, was the cap of a cotton buds packet (see image)

The carton roll, I took it off from a roll of kitchen foil (see image).

The rigid paper came from a colorful paper shopping bag I had spared (see image)

Step 2: Skeleton

To create the skeleton, use the pair of scissors to make a hole at the center of each plastic container, as large as the carton roll you are using (see image).

Then pile the containers in the roll, in descending order of sizes (see image).

Step 3: Background

Draw the contour of a christmas tree on your rigid paper (see image) and cut along these drawn lines (see image).

Attach stripes of your double-sided cellotape, along the branches of the tree (see image).

Use the cellotape to fix the green veiled paper over your rigid paper (see image).

Step 4: Fixing Background and Skeleton Together

To fix the paper-made christmas tree at the back of the skeleton, place the tree under the skeleton, in the position you wish to fix it. Create 2 holes in correspondence of the 2 corners of the bottom container and of the paper-made tree. Let the ribbon pass through these holes and make a bow with it, for both the left and right holes.

Similarly, create an hole in the top container and in the corresponding are of the paper-made tree; then let another ribbon pass through the holes. Make a nod at the two extremes of the ribbon. This will be used to hang the calendar (see image).

Eventually, also draw and cut a star from the rigid paper. Make 2 holes in it and in the top container in the areas corresponding to where you want the star to be places. Let another ribbon pass through these holes and make with it, another bow.

Step 5: Baking

Finally cook your cookies/sweets and/or write some notes for each one of the 25 days of advent.
I baked the Apple-Core healthy cookies, for instance.

Then wrap each of them in one of the christmas napkin. Use the ribbon to close the napkins shaped as a sachet and stick an adhesive on them, on which you'll have written the days numbers from 1 to 25. Place them in the plastic containers from the bottom to the top, in ascendin order of numbers.