I glued the flower die onto the paper first and then die-cut the largest heart of my set. I die-cut the "thanks" sentiment and glued it to the heart flower card base. I also die-cut another heart, put it on my scoring board and scored the heart panel about 1/2 inch from the top, making sure the fold was flat by pressing my bone folder on the fold. I glued the finished top to the 1/2 inch folded heart top, lining up the panels and pressing to seal the panels. It's really a much easier card than my description makes it.
Here I used an Altenew Heart die, the Hero Arts largest heart is 4.66 X 4.11" and your card would be much larger.
Hero Arts Flower Garden Fancy Die
Hero Arts Thanks Stamp and Cut set
Altenew Halftone Hearts Nesting Die Set
Hero Arts Nesting Hearts Infinity Dies (not used here, but bigger range of sizes.
Martha Stewart Scoring board
Vagabond die cut machine