The original link from this pin is broken, but this DIY looks fairly simple. This could be done on canvas, board, wood, anything that is stiff. Paint it red and place white letter decals on top. If you don't want to do decals, you can always paint the letters in white - which might require a few coats.
Wrap the middle of the board with red and white baker's twine, and tie on the heart, punched out of patterned card stock.