For best results, use a crisp (new) bill which will hold the folds better.
Fold diagonally, doesn't matter which side.
Fold diagonally again in other direction.
Fold down to create square.
Fold diagonally again, doesn't matter which side.
Bend both left & right sides inward like image.
Fold both tips upward toward the center.
Fold both sides (the wings) vertically toward the center. Note-it won't quite reach the center.
Fold at very bottom. For clarification, this is the BACK of the heart.
Flip to the other side which is the FACE of the heart & fold the top downward away from the 2 tips.
Fold tips sideways to the front to create top shape of heart.
Insert the very tip into the slot. Note-the tips won't stay put because its so little.
What it should look like so far.
Flip to the BACK again where we left off so far.
This is what it looks like if you flatten it.
Fold the top extra border down inward to reveal the top of heart.
Flip to the FRONT and fold the bottom corners toward the center.
Tuck the corners into the slot again (slot shown where toothpick is). Do both corners & you're done.
Completed back image.
Completed front image. Lay a heavy book on top for a couple days and the tips will stay put in slot. Left one was made a very long time ago so it stays & looks flatter compared to new one at right.
Video tutorial per viewers' request. Steps 2-9