Reverse Picture Frame
Start by painting the frame black. I only painted the front and sides, which is fine if you're going to display the frame against a wall. Paint the back also if you'll be putting the frame on a tabletop where the back is visible.
When the paint is dry, arrange the photos to fit on the wood part of the frame. It's OK if part of a photo hangs over into the opening as long as the faces are not going to be cut off. When you're happy with how they look, adhere them lightly to the frame. Use repositionable tape or a small amount of permanent tape. As you can see, I added a small rectangle to the right of the heart to hold the space for where I'd write the date.
Turn the frame upside down. Use a Sharpie to trace the shape of the cut-out heart.
Turn the frame right-side up. Remove each photo that overlaps into the cut-out heart and trim just inside the Sharpie line. That will leave a tiny border of black on the frame. Use a strong adhesive to secure all photos to the frame. You could use a sealant over the top if you want it to be very durable, but I just left it as is.
Cut a piece of cardstock to fit inside the cut-out heart. Add a title with letter stickers, then insert it into the frame.
I love how it turned out!