Answer: You might be able to sprinkle seeds onto home made paper (while it is still in the wet stage) that is subsequently dried normally and then cut into a heart shape. Guests could then "plant" the paper and the seeds along with it. I would suggest you experiment with this and see if the result is acceptable.
A thicker medium could potentially cause the seeds to become overly damp and begin to germinate, then they would rot before the "dough" dries.
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