stalagmite technique? could vary the size, but tissue paper is so much cheaper than the spray foam. Not necessarily flowers but something else in giant size? - Giant Tissue Flower | Tutorial (some steps):
City of Gomez Palacio: Top in the building of the disappeared Factory of Yarns and Tissues "La Amistad". (Ciudad de Gómez Palacio: Remate en el Edificio de la desaparecida Fábrica de Hilados y Tejidos "La Amistad".