Lay the paper pattern side down (illustrated as dark pink). Fold sheet in half along the diagonal (see A); smooth with a bone folder. Unfold sheet. Fold it in half along the opposite diagonal; smooth with a bone folder. Unfold sheet so that the pattern side faces down.

Using a wide acrylic ruler (or a standard ruler), measure 4 inches in from the left side of square; score vertically along ruler with a bone folder. Fold left flap in along scored line (see B); smooth with bone folder. Repeat on right side of square, measuring 4 inches in, scoring vertically and folding in right flap (see C). Unfold both flaps. Repeat on top and bottom of square, measuring 4 inches in from both sides, scoring horizontally, and folding in both flaps. Unfold both flaps. (At this point, the paper is divided into 9 small squares.)

Flip sheet so that the pattern side faces up. Bring the upper right corner of the paper to meet the lower left corner of the center small square (see D). Fold along the diagonal of the square above the center square (where the arrow is); smooth with bone folder. Unfold, and rotate the sheet 90 degrees. Repeat entire process, starting at what is now the upper left corner of the sheet and continuing as indicated above. Rotate, and repeat 2 more times to make 4 folds total.

Unfold sheet so that the pattern faces down. (See E for a diagram of the fold directions. The 4 peaked folds are indicated by the red dotted lines; all the others are receding folds.) Grasp opposite corners, placing your index fingers inside the valleys, with the thumbs and other fingers supporting both sides of the corners. Gently bring corners slightly toward center of paper, letting the folds peak and recede naturally.

Maneuver as needed until the sheet folds into a 4-pointed pinwheel shape, with a small square in the center (see F).

Working with 1 flap at a time and moving counterclockwise, fold down the first 3 pinwheel flaps onto center square of pinwheel; each folded flap should overlap the one before it (see G). Fold in final flap, and slip beneath first flap to hold the resulting 4-inch square closed (see H).

To decorate valentine: On the front of the folded square, add a decorative embellishment, such as a painted heart. If you're including a poem or greeting, write the opening lines along the outer 4 edges, numbering 1 through 4 to orient the reader. Let dry if needed. Open flaps to the pinwheel shape; add embellishments to the center square of pinwheel, and continue to write lines of text along the diagonal of each flap, numbering accordingly. Open sheet fully; add embellishments to center square, and write remaining lines of text along desired fold lines, numbering accordingly. If desired, place a 3 3/4-inch square note, photo, or other enclosure atop interior center square. The secret addition will be hidden inside the refolded valentine as a surprise for the recipient.