Step 1:
The white paper is standard printer/copy paper.

Step 2:
Fold the white paper in half over this line.

Step 3:
Prefold over these 4 lines

Step 4:
Pull the 4 corners upwards by folding over these 4 sets of 3 blue lines. The edges are folded upwards over the prefolded yellow lines while you do this.

Step 5:
Push the 2 layers of the flap against each other, see yellow arrows. Then lock them together by making a valley-fold over the blue line.

Do the same with the other 3 flaps.

Step 6:
This part of the pencil box is done....

Step 7:
Prefold the pink paper over these 4 lines. Use the white box as guidance to place these folds.
Then, rotate the pink paper 90 degrees

Step 8:
Valley-fold over these 2 lines.
Use the white box as guidance again.

Step 9:
Valley-fold over these 4 lines, they are prefolded in step 7

Step 10:
Slide the edge on the left under the edges indicated by the 2 arrows.

Step 11:
Slide the white box in the pink polka dot part.