Score the folds on the square annex building. Note that two of the folds are reverse folds (score on the back).

The long extension from the side of the annex is folded back on itself to make a thick wall, as shown in the right side of the diagram.

Fold the main part of the annex into a box shape.

Cut out the largest oval section. Roll the walls against a round dowel or pencil to curl the walls into an oval shape matching the curvature of the oval roof. Glue the walls together and then the roof in place.

Glue the square annex to the rear of the oval base section. Reach underneath the building with a tweezer to squeeze the two pieces together to set the glue.

Assemble the smaller oval tiers of the building in the same way as the base section. Glue each tier to the top of the previous section. Note that the three lower tiers should line up flush at the back of the building, while the small top tier is centered within the roof.