I drew my heart shape and carved it out.
If I could do it again, I would carve the sides at an angle. The edges came out rather square.
I placed a piece of plywood on the bottom and oiled the bottom and sides with oil to keep the concrete from sticking to the foam and board.
I mixed and poured the concrete. I must say that I had trouble with this step, never having worked with cement before, the cement mix was fine and it also contained small rocks. I wasn't sure whether to leave out the small rocks and use the fine dust or if a mix of both was necessary? So I had lots of texture, but it could have been from too much water. Not sure.