1. Material: one-color cardboard three times the size of A4 paper, A4 paper, transparent thin file bag.

2. Divide a piece of one-color cardboard which is three times the size of A4 paper into three equal parts, draw lines, then fold the left part inward according to the separation line, and then fold the right part inward according to the separation line to make it the size of A4 paper.

3. Draw a box on the right side of the folded cardboard, and each side should be about three centimeters away from the edge of the cardboard. Then cut off the frame, draw a semicircle on the right side of the whole cardboard, and cut it off.

4. On a piece of A4 paper, draw with a pencil, then color it, and finally erase the imprint of the pencil.

5. Put the painted paper on the top left of the transparent thin file bag, and then cut off the part of the file bag larger than A4 paper. Fix the back of the painting in the file bag.