This Valentine pop up card is easier to construct than you would think.
For want of a better name, I call these "meet in the middle" pop up cards.
Half of the design is cut from either side of the card and the two pieces are slotted together.
This card is really an elaborate variation of the slotted X mechanism.
The slotted X is covered in How to Make Pop Up Cards, Lessons 11 - 15 .
How to make the pile of hearts Valentine pop up card
Download and cut out template.
The file set includes score lines for the center fold, and tiny score lines at the heart points. I suggest turning OFF those tiny lines if you are a machine cutter who uses a dotted cut, dash cut, or kiss cut. (My hearts ripped off when I used a dotted cut.) The hearts will fold up easily enough without scoring, or you can hand score.
Download file set: PDF, Silhouette studio, SVG (how to use my SVG files in Cricut Design Space), Silhouette Studio.
Files download for free; pay what you wish for the tutorial and to support this site. Suggested contribution for this project is $1.99.
Remove the large heart that lies on the center fold. Use it on the front of your card or discard.
Crease the fold lines at the heart bottoms, folding both piles of hearts toward the center foldline.
The two halves of the (white) card are purposely cut apart at the center "fold." If you had a fold here you will get a wrinkle when the card is closed due to bulk. I learned that the hard way, you can see the wrinkle in my photos!
Optional: back the cut out with patterned paper before gluing to the base card. I used a red striped paper. Be careful not to get glue on the hearts, just the part they were cut from!
Adhere the two heart halves (white) to the base card (red), leaving a tiny gap between them along the center fold of the base card. Take care not to get glue on the hearts.
Here's one by Molly Lee to show you what I'm talking about.
Pull the hearts toward each other and slot together above the center fold of the card.
The card lies flat when opened.
More about how this card works for the mathematically inclined....
The measurement from the center fold of the card to the crease line of the hearts is the same on both sides of the center fold. (Shown in red.)
If you draw a line from the end point of one slot to the end point of the other, you have a straight line perpendicular to the center fold. And each end point is at equal distance from the center fold. (Shown in blue).